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Published on: 26/09/2019
Factorisation
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1.
Divide: 81x3(50x2 - 98) by 27x2(5x + 7)
2.
Simplify: - 45p3 + 9p2
3.
Divide 63(p4 + 5p3 - 24p2) by 9p(p + 8).
4.
Factorise: x - 9 + 9zy - xyz
5.
factorise: ax3y2+bx2y3+cx2y2z
6.
Factorise: 27x3 - 21x2 + 15x4
7.
Find and correct the errors in the following mathematical statements 2x+ 3y= 5xy
8.
If the expression (x2 + 19x - 20) shows the area of rectangle. Find the possible length and breadth of this rectangle.
9.
Factorise the expressions and divide them as directed.
(5p2 -25p+ 20)÷(p- 1)
10.
Foetorise the following expressions. p4 - 81
11.
Foetorise the following expressions.a4 - b4
12.
Factorise the following expressions. 25m2 + 30m + p
13.
Factorise the following expressions.p2 - 10p + 25
14.
factorise the following expressions. -16z + 20z3
15.
factorise the following expressions. 7a2 + 14a
1.
We have 50x2 - 98 = 2(25x2 - 49)
= 2[(5x)2 - (7)2] == 2[(5x + 7)(5x - 7)] [Using a2 - b2 = (a + b)(a - b)]
= \(\frac { 81x^{ 3 }[50x^{ 2 }-98] }{ 27x^{ 2 }[5x+7] } \)
=\(\frac { { 81x }^{ 3 } }{ { 27x }^{ 2 } } \left[ \frac { 2(5x-7)(5x+7) }{ (5x+7) } \right] =3x[2(5x-7)]\)
= 3x\(\times \)2\(\times \)(5x- 7) = 6 x (5x - 7)
2.
We have -45p3
= (-1) x 3 x 3 x 5 x P x P x P
9p2 = 3 x 3 x p x p
∴ [- 45p3] + 9p2 = [(-1) x 3 x 3 x 5 x P xP x p] \(\div \) (3 x 3 x p x p)
=\(\frac { (-1)\times 3\times 3\times 5\times P\times P\times P }{ 3\times 3\times p\times p } \)
=\(\frac { -1\times 5\times P }{ 1\times 1 } =-1\times 5p=-5p\)
3.
We have 63(p4 + 5p3 - 24p2) + 9p(P + 8)
= \(\frac { 63({ p }^{ 4 }+5p^{ 3 }-24p^{ 2 } }{ 9p(p+8) } \)
= \(\frac { 63p^{ 2 }(p^{ 2 }+5p-24) }{ 9p(p+8) } \)
= \(\frac { 63p^{ 2 } }{ 9p } \)
= \(\left[ \frac { { p }^{ 2 }8p-3p-24 }{ p+8 } \right] \)
= \(7p\left[ \frac { p(p+8)-3(p+8) }{ (p+8) } \right] \)
= \(7p\left[ \frac { (p+8)(p-3) }{ (p+8) } \right] =7p(p-3)\)
4.
By regrouping, we have
x - 9 + 9zy - xyz = x - 9 - xyz + 9zy
= 1(x - 9) - yz(x - 9) = (x - 9)(1 - yz)
5.
we have ax3y2=a\(\times \)x\(\times \)x\(\times \)x\(\times \)y\(\times \)y
bx2y3=b\(\times \)x\(\times \)x\(\times \)y\(\times \)y\(\times \)y
cx2y2z=c\(\times \)x\(\times \)x\(\times \) y\(\times \)y\(\times \)z
Obviously, x2y2 is a common factor.
ஃ we get ax3y2=x2y2\(\times \)a\(\times \)
bx2y3=x2y2\(\times \)b\(\times \)y
cx2y2z=x2y2\(\times \)c\(\times \)z
\(\Rightarrow \) ax3y2+bx2y3+cx2y2z
= [(x2y2\(\times \)a\(\times \)x)+(x2\(\times \)y2\(\times \)b\(\times \)y) + x2y2\(\times \) c\(\times \) z)]
= x2y2[(a\(\times \)x)+(b\(\times \)y)+(c\(\times \)z)]
= x2y2(ax + by + cz)
6.
We have 27x3 = 3 x 3 x 3 \(\times \)x\(\times \)x\(\times \)x
21x2 = 3\(\times \)7\(\times \)x\(\times \)x
15x4 = 3 x 5 \(\times \) x \(\times \) x \(\times \) x \(\times \) x
We get common factors as 3, x and x.
i.e., 3 \(\times \) x \(\times \)x or 3x2
∴27x3 =: 3x2 x 3 \(\times \) x \(\times \) 3 = 3x2 \(\times \)9x
21x2=\({ 3x }^{ 2 }\times 7={ 3x }^{ 2 }\times 7\)
\({ 15x }^{ 4 }=3x^{ 2 }\times 5x\times x={ 3x }^{ 2 }\times { 5x }^{ 2 }\)
\(\Rightarrow { 27x }^{ 3 }-{ 21x }^{ 2 }+{ 15x }^{ 4 }\)
\(\Rightarrow { (3x }^{ 2 }\times 9x)-({ 3x }^{ 2 }\times 7)+{ (3x }^{ 2 }\times { 5x }^{ 2 })\)
\({ 3x }^{ 2 }[9x-7+{ 5x }^{ 2 }]\)
7.
Given mathematical statement is incorrect.
Hence, correct statement is 2x + 3y = 2x + 3y because in both terms, variables are different and we can add only like terms
8.
It is given that, the expression (x2 + 19x - 20) shows the area of rectangle. To find the possible length and breadth of this rectangle. We have to factorise (x2 + 19x - 20).
Since, -1 and 20 are integers such that
-1 x 20 = - 20 and 20 + (-1) = 19
Putting these values in given expression
x2 + (20 -1) x - 20 = x2 + 20x - x - 20
= x (x + 20) -1 (x + 20)
=(x + 20) (x -1)
Hence, possible length and breadth of this rectangle will be (x + 20) and (x -1).
9.
Here, 5P2-25P+20 = 5(p2-5P + 4)
= 5[p2 +(-4-1)p+4]
= 5(p2-4p-P+ 4) [∵ ab = 4 and a + b= -5, ஃ a= -4, b= -1]
= 5[p(p-4)-1(p-4)]
= 5(p-4)(p-1)
Now, (5p2-25p + 20) ÷ (p-1)
=\(\frac{5p^{2}-25p+20}{(p-1)}\)
=\(\frac{5(p-4)(p-1)}{(p-1)}=5(p-4)\)
10.
p4 -81=(p2)2 -(9)2
On comparing with a2 - b2, we get a = p2 and b = 9
p4 -81 = (p2 + 9)(p2 -9)
[\(\therefore\) (a2 -b2) = (a + b)(a - b)]
= (p2- 9) [(p)2 - (3)2]
= (p2+ 9) (p + 3 (p - 3)
[\(\because\) a2-b2 =(a+b)(a-b) and (p2 + 9) cannot be factorised further]
11.
a4-b4 = (a2)2-(b2)2
Oncomparing with a2 - b2, we get a = a2 and b = b2
\(\therefore\) a4 -b4 = (a2 +b2)(a2 -b2)
= (a2 + b2 )(a + b)(a - b) [\(\because\) a2-b2 = (a + b)(a - b)] and a2 + b2 cannot be factorised further
12.
25m2 + 30m + 9 = (5m)2 + 30m + (3)2
= (5m)2 + 2(5)m (3) + (3)2
This expression is of the form a2 + 2ab + b2.
On comparing, we get a = 5m and b = 3
Since, a2 + 2ab + b2 = (a + b)2
\(\therefore\) 25m2 + 30m + 9 = (5m + 3)2 or (5m + 3)(5m + 3)
13.
p2 -l0p + 25 = (p)2 -l0p + (5f = p2 - 2(5)p + 52
This expression is of the form a 2 - 2ab + b2 .
On comparing, we get a = p and b = 5
Since, a2 - 2ab + b2 = (a - b)2
\(\therefore\) p2 -10p+25=(p-5)2 or (p-5)p-52
14.
we have -16z = (-1) x 2 x 2 x 2 x 2 x z
and 20z3 = 2 x 2 x 5 x z x z X z
The two terms have 2, 2 and z as common factors
Therefore, -16z + 20z3 = (-1) x 2 x 2 x 2 x 2 x z x 2 x 2 x 2 x 5 x z x z x z
= 2 x 2 x z [(-1) x 2 x 2 + 5 x z x z] [combining the terms]
= 4z (-4 + 5z2)
15.
we have 7a2 = 7 x a x a and 14a = 2 x 7 x a
the two terms have 7 and as common factors
therefore. 7a2 + 14a = 7 x a x a + 2 x 7 x a
= 7 x a (a+2) [combining the terms]
= 7 a (a + 2)
It is the required factor form
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