Given y = x⁴ + 2x² - x
\(\frac { dy }{ dx } \) = 4x³ + 4x - 1
Slope of the tangent at x = 1 is
m = \(\left( \frac { dy }{ dx } \right) \)(x = 1)
= 4(1)³+ 4 (1) - 1
= 4+4-1 = 7
∴ m = 7

We know that sin^-1: [-1, 1] \(\rightarrow \left[ -\frac { \pi }{ 2 } ,\frac { \pi }{ 2 } \right] \)is given by
sin⁻¹x = y if and only if x = sin y for −1\(\le x\le \) and -\(\frac { \pi }{ 2 } \le y \le \frac { \pi }{ 2 } \). Thus
\({ sin }^{ -1 }\left( sin\left( \frac { 5\pi }{ 6 } \right) \right) \)= \({ sin }^{ -1 }\left( sin\left( \frac { \pi }{ 6 } \right) \right) \) = \({ sin }^{ -1 }\left( sin\frac { \pi }{ 6 } \right) \), since \(\frac{\pi}{6}\)\(\in \left[ -\frac { \pi }{ 2 } ,\frac { \pi }{ 2 } \right] \)

Let z = -6+8i
|z| =\(\sqrt { (-6)^{ 2 }+8^{ 2 } } \)
= \(\sqrt { 36+64 } =\sqrt { 100 } \) = 10
\(\sqrt { a+ib } =\pm \left( \sqrt { \frac { |z|+a }{ 2 } } +i\frac { b }{ |b| } \sqrt { \frac { |z|-a }{ 2 } } \right) \)
[Here |z| = 10, a = -6, b = 8]
\(\sqrt { -6+8i } \pm \left( \sqrt { \frac { 10-6 }{ 2 } } +i\frac { 8 }{ |8| } \sqrt { \frac { 10+6 }{ 2 } } \right) \)
= \(\pm \left( \sqrt { \frac { 4 }{ 2 } } +i\sqrt { \frac { 16 }{ 2 } } \right) \)
= \(\pm (\sqrt { 2 } +i\sqrt { 8 } )\)
= \(\\ \pm (\sqrt { 2 } +i2\sqrt { 2 } )\)
Aliter :
Square root of -6 + 8i
Let a + ib = - 6 + 8i
a = -6, b = 8
\(|z|=\sqrt{6^{2}+8^{2}}=\sqrt{100}=10\)
\(\sqrt{a+i b}=\pm\left[\sqrt{\frac{\sqrt{a^{2}+b^{2}}+a}{2}}+i \frac{b}{|b|} \sqrt{\frac{\sqrt{a^{2}+b^{2}}-a}{2}}\right]\)
\(=\pm\left[\sqrt{\frac{10-6}{2}}+i \sqrt{\frac{10+6}{2}}\right]\)
\(=\pm[\sqrt{2}+i \quad 2 \sqrt{2}]\)

Given \(\vec { a } =\hat { i } -2\hat { j } +3\hat { k }, \vec { b } =2\hat { i } +\hat { j } -2\hat { k }, \vec { c } =3\hat { i } +2\hat { j } +\hat { k } \)
∴ \(\vec { a } .(\vec { b } \times \vec { c } )=\left| \begin{matrix} 1 & -2 & 3 \\ 2 & 1 & -2 \\ 3 & 2 & 1 \end{matrix} \right| \)
= \(1\left| \begin{matrix} 1 & -2 \\ 2 & 1 \end{matrix} \right| +2\left| \begin{matrix} 2 & -2 \\ 3 & 1 \end{matrix} \right| +3\left| \begin{matrix} 2 & 1 \\ 3 & 2 \end{matrix} \right| \)
= 1(1+4)+2(2+6)+3(4-3)
= 1(5)+2(8)+3(1)
= 5+16+3 = 24
\(\vec { a } .(\vec { b } \times \vec { c } )\) = 24

Here A = 3, B = 0, C = 3, D = -4, E = 3 and F = 10
A = C and B = 0 (No xy term)
Hence, the given equations represents a circle.

\(\left| \frac { 2+i }{ -1+2i } \right| =\frac { \left| 2+i \right| }{ \left| -1+2i \right| } =\frac { \sqrt { { 2 }^{ 2 }+{ 1 }^{ 2 } } }{ \sqrt { \left( -1 \right) ^{ 2 }+{ 2 }^{ 2 } } } =1\) \(\left( \because \left| \frac { { z }_{ 1 } }{ { z }_{ 2 } } \right| =\left| \frac { { z }_{ 1 } }{ { z }_{ 2 } } \right| ,{ z }_{ 2 }\neq 0 \right) \)

Here Δ = b²−4ac = 0 for equal roots. This implies 4(k + 2)² = 4(9)k. This implies k = 4 or 1.

Let sin^-1 \(\left( -\frac { 1 }{ 2 } \right) \) = y. Then sin y = -\(\frac{1}{2}\)
The range of the principal value of sin^-1x is \(\left[ -\frac { \pi }{ 2 } ,\frac { \pi }{ 2 } \right] \) and hence, Let us find y \(\in \left[ -\frac { \pi }{ 2 } ,\frac { \pi }{ 2 } \right] \) Such that sin y = -\(\frac{1}{2}\). Clearly, y = -\(\frac{\pi}{6}\)
Thus, the principal value of sin^-1\(\left( -\frac { 1 }{ 2 } \right) \) is -\(\frac{\pi}{6}\). This corresponds to -30^o.

Taking (x₁, y₁) as (2, 3), we get
x₁² + y₁² + 2gx₁+ 2fy₁+ c = 2² + 3² − 6 × 2 − 8 × 3 + 12 
= 4 + 9 - 12 - 24 + 12
= -11\(<\)0.
Therefore the point (2, 3) lies inside the circle, by theorem.

Equation of the circle in standard form is (xr − h)² + (y − k)² = r²
\( \Rightarrow (x-(-3))^{2}+(y-(-4))^{2} =3^{2} \)
\( \Rightarrow (x+3)^{2}+(y+4)^{2} =3^{2} \)
\( \Rightarrow x^{2}+y^{2}+6 x+8 y+16 =0 .\)

We first find adj A. By definition, we get adj A = \({ \left[ \begin{matrix} +{ M }_{ 11 } & -{ M }_{ 12 } \\ -{ M }_{ 21 } & +{ M }_{ 22 } \end{matrix} \right] }^{ T }={ \left[ \begin{matrix} d & -c \\ -b & a \end{matrix} \right] }^{ T }=\left[ \begin{matrix} d & -c \\ -c & a \end{matrix} \right] \).
Since A is non-singular, |A| = ad - bc ≠ 0.
As \({ A }^{ -1 }=\frac { 1 }{ \left| A \right| } \) adj A, we get A^-1 = \(\frac { 1 }{ ad-bc } \left[ \begin{matrix} d & -b \\ -c & a \end{matrix} \right] \).

Since α, β, and γ are the roots of the equation x³+ px²+ qx + r = 0, we have
Σ₁ α + β + γ = -p and Σ₃ αβγ = -r
\(\Sigma \frac { 1 }{ \beta \gamma } =\frac { 1 }{ \beta \gamma } +\frac { 1 }{ \gamma \alpha } +\frac { 1 }{ \alpha \beta } =\frac { \alpha +\beta +\gamma }{ \alpha \beta \gamma } =\frac { -p }{ -r } =\frac { p }{ r } \).

Given g(x, y) = 3x² + y² + 5x + 2
\(\frac { { \partial }g }{ { \partial x } } \) = 6x + 0+ 5 = 6x + 5
\({ \left( \frac { { \partial }g }{ { \partial x } } \right) }_{ (1,-2) }\) = 6(1) + 5 = 11
\(\frac { { \partial }g }{ { \partial y } } \) = 0 + 2y + 0 + 0 = 2y
\(\therefore { \left( \frac { { \partial }g }{ { \partial y } } \right) }_{ (1,-2) }\) = 2(-2) = -4

\(\underset { x\rightarrow \infty }{ lim } \frac { { 2x }^{ 2 }-3 }{ { x }^{ 2 }-5x+3 } =\frac { 2-\frac { 3 }{ { x }^{ 2 } } }{ 1+\frac { 5 }{ x } +\frac { 3 }{ { x }^{ 2 } } } \)
[Dividing the numerator and denominator by x²]
= \(\frac { 2-0 }{ 1-0+0 } =\frac { 2 }{ 1 } =2\)

\(3-i\sqrt { 3 } \)
Let x + iy = \(3-i\sqrt { 3 } \)
= r(cos θ + i sin θ)
r = \(\\ \sqrt { { x }^{ 2 }+{ y }^{ 2 } } =\sqrt { 3^{ 2 }+(\sqrt { 3 } )^{ 2 } } =\sqrt { 9+3 } \)
= \(\sqrt { 12 } =2\sqrt { 3 } \)
α = \(tan^{ -1 }\left| \frac { y }{ x } \right| =tan^{ -1 }\left| \frac { -\sqrt { 3 } }{ 3 } \right| =tan^{ -1 }\left| \frac { 1 }{ \sqrt { 3 } } \right| =\frac { \pi }{ 6 } \)
Since the complex number \(3-i\sqrt { 3 } \) lies in the IV quadrant, [∵ x ⟶ +ve y ⟶ -ve]
Its principal value θ = -α
⇒ θ = \(\frac { \pi }{ 6 } \)
∴ Its polar form is
\(3-i\sqrt { 3 } \) = 2\(\sqrt { 3 } \)\(\left[ cos\left( 2k\pi -\frac { \pi }{ 6 } \right) +isin\left( 2k\pi -\frac { \pi }{ 6 } \right) \right] ,k\in Z\)

LHS =  \(\cfrac { a+b\omega +c{ \omega }^{ 2 } }{ b+c\omega +{ a\omega }^{ 2 } } +\cfrac { a+b\omega +{ c\omega }^{ 2 } }{ c+a\omega +b{ \omega }^{ 2 } } \)
\(\cfrac { a\omega ^{ 3 }+b\omega +c{ \omega }^{ 2 } }{ b+c\omega +{ a\omega }^{ 2 } } +\cfrac { a\omega ^{ 3 }+b\omega ({ \omega }^{ 3 })+{ c\omega }^{ 2 } }{ c+a\omega +b{ \omega }^{ 2 } } \) [∵ ω³ = 1]

= ω + ω² = -1              [ ∵ 1 + ω + ω² = 0]

\({ tan }^{ -1 }(\frac { 2 }{ 11 }) +{ tan }^{ -1 }(\frac { 7 }{ 24 }) ={ tan }^{ -1 }(\frac { 1 }{ 2 } )\)
\(LHS={ tan }^{ -1 }\left( \frac { 2 }{ 11 } \right) +{ tan }^{ -1 }\left( \frac { 7 }{ 24 } \right) \)
= \({ tan }^{ -1 }\left( \frac { \frac { 2 }{ 11 } +\frac { 7 }{ 24 } }{ 1-\left( \frac { 2 }{ 11 } \right) \left( \frac { 7 }{ 24 } \right) } \right) \) \(\left[ \because { tan }^{ -1 }(x)+{ tan }^{ -1 }y={ tan }^{ -1 }\left( \frac { x+y }{ 1-xy } \right) \right] \)
= \({ tan }^{ -1 }\left( \frac { \frac { 48+77 }{ 11\times 24 } }{ \frac { 264-14 }{ 264 } } \right) ={ tan }^{ -1 }\left( \frac { \frac { 125 }{ 264 } }{ \frac { 250 }{ 264 } } \right) \)

= RHS
Hence proved.

Let A = \(\left[ \begin{matrix} 1 & 2 & 3 \\ 2 & 1 & 4 \\ 3 & 0 & 5 \end{matrix} \right] \). Applying elementary row operations, we get
A \(\overset { \begin{matrix} { R }_{ 2 }\longrightarrow { R }_{ 2 }-2{ R }_{ 1 } \\ { R }_{ 3 }\longrightarrow { R }_{ 3 }-3{ R }_{ 1 } \end{matrix} }{ \longrightarrow } \left[ \begin{matrix} 1 & 2 & 3 \\ 0 & -3 & -2 \\ 0 & -6 & -4 \end{matrix} \right] \overset { { R }_{ 3 }\longrightarrow { R }_{ 3 }-2{ R }_{ 2 } }{ \longrightarrow } \left[ \begin{matrix} 1 & 2 & 3 \\ 0 & -3 & -2 \\ 0 & 0 & 0 \end{matrix} \right] \).
The last equivalent matrix is in row-echelon form. It has two non-zero rows. So, ρ(A) = 2.

Given that equation of the circle is
x² + y² = 16
⇒ a² = 16
and equation of the tangent is
y = \( 2\sqrt { 2 } \)x + c
⇒ m = \( 2\sqrt { 2 } \)  and c = c
[∵ y = mx + c is the tangent]
The condition for the line y = mx + c is a tangent to the circle x² +y² = a² is
c² = a² (1 + m²)
⇒ c² = 16(1 + \(\left( { \left( 2\sqrt { 2 } \right) }^{ 2 } \right) \)
⇒ c² = 16(1 + 8)
⇒  c² = 16(9)
⇒ c = ± 4(3)
⇒ ±12

Given r = 5 cm

Since the circle touches the x axis, its centre is (0, ±5)
Equation of the circle is (x - h)² + (y - k)² = r²
⇒ (x - 0)² + (y ± 5)² = 25
\(\Rightarrow x^{2}+y^{2}+\not 25 \pm 10 y=\not 25\)
⇒ x²+y²+10y = 0

Given that the height of the tree is 12m.
Let x m be the standing part and (12 -x)m be the broken part.
Given \(x=\sqrt [ 3 ]{ 12-x } \)
\(\Rightarrow x=(12-x)^{ \frac { 1 }{ 3 } }\)


Taking power 3 both sides, we get 
⇒ x³ = 12-x
⇒ x³+ x -12 = 0
which is the required mathematical problem.

x⁸- 3x + 1 = 0
Here a_n = 1, a_o = 1
If \(\frac{p}{q}\) is a root of the polynomial, then as 
(p, q) = 1p is a factor of a_o = 1 and q is a factor of a_n = 1
Since 1 has no factors, the given equation has no rational roots.

  Given \(\vec { a } =2\hat { i } +3\hat { j } -\hat { k } ,\vec { b } =3\hat { i } +5\hat { j } +2\hat { k } \) and \(\vec { c } =-\hat { i } -2\hat { j } +3\hat { k } \)
Consider \((\vec { a } \times \vec { b } )=\left| \begin{matrix} \hat { i } & \hat { j } & \hat { k } \\ 2 & 3 & -1 \\ 3 & 5 & 2 \end{matrix} \right| \)
= \(\hat { i } \left| \begin{matrix} 3 & -1 \\ 5 & 2 \end{matrix} \right| -\hat { j } \left| \begin{matrix} 2 & -1 \\ 3 & 2 \end{matrix} \right| +\hat { k } \left| \begin{matrix} 2 & 3 \\ 3 & 5 \end{matrix} \right| \)
= \(\\ \hat { i } (6+5)-\hat { j } (4+3)+\hat { k } (10-9)=11\hat { i } -7\hat { j } +\hat { k } \)
∴ LHS = \((\vec { a } \times \vec { b } )\times \vec { c } \)
= \(\left| \begin{matrix} \hat { i } & \hat { j } & \hat { k } \\ 2 & 3 & -1 \\ 3 & 5 & 2 \end{matrix} \right| =\hat { i } \left| \begin{matrix} -7 & 1 \\ -2 & 3 \end{matrix} \right| -\hat { j } \left| \begin{matrix} 11 & 1 \\ -1 & 3 \end{matrix} \right| +\hat { k } \left| \begin{matrix} 11 & -7 \\ -1 & -2 \end{matrix} \right| \)
= \(\hat { i } (-21+2)+\hat { j } (33+1)+\hat { k } (-22-7)\)
= \(-19\hat { i } -34\hat { j } -29\hat { k } \) ..............(1)
For RHS
\(\vec { a } .\vec { i } =(2\hat { i } +3\hat { j } -\hat { k } ).(-\hat { i } -2\hat { j } +3\hat { k } )\)
= -2-6-3 = -11
\(\vec { b } .\vec { c } =(3\hat { i } +5\hat { j } +2\hat { k } ).(-\hat { i } -2\hat { j } +3\hat { k } )\)
= -3-10+6 = -7
∴ RHS = \((\vec { a } .\vec { c } )\vec { b } -(\vec { b } .\vec { c } )\vec { a } \)
= \(-11(3\hat { i } +5\hat { j } +2\hat { k } )+7(2\hat { i } +3\hat { j } -\hat { k } )\)
= \(-33\hat { i } -55\hat { j } -22\hat { k } +14\hat { i } +21\hat { j } -7\hat { k } \)
= \(-19\hat { i } -34\hat { j } -29\hat { k } \)  ............... (2)
From (1) & (2), LHS = RHS
Hence \((\vec { a } \times \vec { b } )\times \vec { c } =(\vec { a } .\vec { c } )\vec { b } -(\vec { b } .\vec { c } )\vec { a } \)
(ii) \(\vec { b } \times \vec { c } =\left| \begin{matrix} \hat { i } & \hat { j } & \hat { k } \\ 3 & 5 & 2 \\ -1 & -2 & 3 \end{matrix} \right| \)
= \(\hat { i } \left| \begin{matrix} 5 & 2 \\ -2 & 3 \end{matrix} \right| -\hat { j } \left| \begin{matrix} 3 & 2 \\ -1 & 3 \end{matrix} \right| +\hat { k } \left| \begin{matrix} 3 & 5 \\ -1 & -2 \end{matrix} \right| \)
= \(\hat { i } (15+4)-\hat { j } (9+2)+\hat { k } (-6+5)\)
= \(19\hat { i } -11\hat { j } -\hat { k } \)
∴ \(\vec { a } (\vec { b } \times \vec { c } )=\left| \begin{matrix} \hat { i } & \hat { j } & \hat { k } \\ 2 & 3 & -1 \\ 19 & -11 & -1 \end{matrix} \right| \)
= \(\hat { i } \left| \begin{matrix} 3 & -1 \\ -11 & -1 \end{matrix} \right| -\hat { j } \left| \begin{matrix} 2 & -1 \\ 19 & -1 \end{matrix} \right| +\hat { k } \left| \begin{matrix} 2 & 3 \\ 19 & -11 \end{matrix} \right| \)
= \(\hat { i } (-3-11)-\hat { j } (-2+19)+\hat { k } (-22-57)\)
= \(-14\hat { i } -17\hat { j } -79\hat { k } \) ............(1)
For RHS
\(\vec { a } .\vec { c } =-11\Rightarrow (\vec { a } .\vec { c } )\vec { b } =-11(3\hat { i } +5\hat { j } +2\hat { k } )\)
= -\(33\hat { i } -55\hat { j } -22\hat { k } \)
\(\vec { a } .\vec { b } =(2\hat { i } +3\hat { j } -\hat { k } ).(3\hat { i } +5\hat { j } +2\hat { k } )\)
= 6+15-2 = 19
\((\vec { a } .\vec { b } )\vec { c } =19(-\hat { i } -2\hat { j } +3\hat { k } )=-19\hat { i } -38\hat { j } +57\hat { k } \)
RHS = \((\vec { a } .\vec { c } )\vec { b } -(\vec { a } .\vec { b } )\vec { c } \)
= \(-33\hat { i } -55\hat { j } -22\hat { k } -(-19\hat { i } -38\hat { j } +57\hat { k } )\)
= \(-14\hat { i } -17\hat { j } -79\hat { k } \) ............(2)
From (1) & (2), LHS = RHS
∴ \(\vec { a } \times (\vec { b } \times \vec { c } )=(\vec { a } .\vec { c } )\vec { b } -(\vec { a } .\vec { b } )\vec { c } \)

tan^-1 \(\left( \frac { 1-x }{ 1+x } \right) =\frac { 1 }{ 2 } { tan }^{ -1 }\)x gives tan^-1 1-tan^-1 x = \(\frac{1}{2}\)tan^-1x. 
Therefore, \(\frac{\pi}{4}=\frac{3}{2}tan^{-1}\)x, which in turn reduces to tan⁻¹ = \(\frac{\pi}{6}\)
Thus, x = tan\(\frac{\pi}{6}=\frac{1}{\sqrt3}\)

Rearrange the terms as
(2x-1)(2x+ 3) (x + 3) (x - 2) + 20 = 0
⇒ (4x² + 6x - 2x- 3)(x² - 2x + 3x - 6) + 20 = 0
⇒ (4x² + 4x - 3) (x² + x - 6) + 20 = 0
put x²+ x = y
⇒ (4y - 3) (y - 6) + 20 = 0
⇒ 4y² - 24y - 3y + 18 + 20 = 0
⇒ 4y²-27y +38 = 0
⇒ (y - 2)( 4y - 19) = 0
\(y=2,\frac { 19 }{ 4 } \)

Case (i) 
When y = 2
x²+ x = 2
x² + x - 2 = 0
⇒ (x + 2)(x - 1) = 0
⇒ x = -2, 1
Case (ii) 
When \(y=\frac { 19 }{ 4 } ,{ x }^{ 2 }+x=\frac { 19 }{ 4 } \)
\(\Rightarrow { 4x }^{ 2 }+4x=19\)
\(\Rightarrow { 4x }^{ 2 }-4x-19=0\)
\(\Rightarrow x=\frac { -4\pm \sqrt { 16-4(4)(-19) } }{ 8 } \)
\(\Rightarrow x=\frac { -4\pm \sqrt { 16+304 } }{ 8 } \)
\(\Rightarrow x=\frac { -4\pm \sqrt { 320 } }{ 8 } \)
\(\Rightarrow x=\frac { 4\pm 8\sqrt { 5 } }{ 8 } \)
\(\Rightarrow x=\frac { -4(-1\pm 2\sqrt { 5 } ) }{ 8 } \)
\(\frac{-1 \pm 2 \sqrt{5}}{2}\)
Hence the roots are 1, -2, \(\frac{-1 \pm 2 \sqrt{5}}{2}\)