Given A = {5,6,7,8}. Which one of the following is incorrect?

(a)

Ø ⊆ A

(b)

A⊆A

(c)

{7,8,9}⊆A

(d)

{5}⊆A

Let R be the relation over the set of all straight lines in a plane such that l₁Rl₂ ⇔ l₁丄l₂ . Then  R is __________

(a)

symmetric

(b)

reflexive

(c)

transitive

(d)

an equivalent relation

Which of the following functions from z to itself are bijections (one-one and onto)?

(a)

f(x) = x³

(b)

f(x) = x + 2

(c)

f(x) = 2x + 1

(d)

f(x) = x² + 1

If \(f:R\rightarrow R\) is defined by \(f(x)=2x-3\) __________

(a)

\({1\over 2x-3}\)

(b)

\({1\over 2x+3}\)

(c)

\({x+3\over 2}\)

(d)

\({x-3\over 2}\)

If \(f(x)={1-x\over 1+x},(x\neq0)\) then f^-1(x) =

(a)

f(x)

(b)

\(1\over f(x)\)

(c)

-f(x)

(d)

-\(1\over f(x)\)