Practicing Success

Target Exam

CUET

Subject

-- Mathematics - Section B1

Chapter

Determinants

Question:

If $f:[3, \infty) \rightarrow$ A defined by $f(x)=x^2$ is an onto function, then $A$ is :

Options:

$R$

$[5, \infty)$

$[6, \infty)$

$[9, \infty)$

Correct Answer:

$[9, \infty)$

Explanation:

f : [3, ∞) → A

f is onto so every image in A must have atleast one pre-image

$f(x) = x^2$

for boundary conditions

$f(3) = 9$           $\lim\limits_{x \rightarrow \infty} f(x) \rightarrow \infty$

so   A = [9, ∞)