Target Exam

CUET

Subject

-- Applied Mathematics - Section B2

Chapter

Calculus

Question:

Find the maximum and the minimum values (if any) of the function $f(x) = 16x^2 - 16x+28$.

Options:

Maximum value: None; Minimum value: 24

Maximum value: 24; Minimum value: None

Maximum value: 28; Minimum value: 24

Maximum value: None; Minimum value: 28

Correct Answer:

Maximum value: None; Minimum value: 24

Explanation:

The correct answer is Option (1) → Maximum value: None; Minimum value: 24

Given $f(x) = 16x^2 - 16x + 28 = 16\left(x^2-x+\frac{7}{4}\right)$

$= 16\left[\left(x^2 - x + \frac{1}{4}\right) + \frac{7}{4} -\frac{1}{4}\right] = 16\left[\left(x − \frac{1}{2}\right)^2 + \frac{3}{2}\right]$

$≥16\left(0+\frac{3}{2}\right)$, for all $x ∈ R$  $(∵(x-\frac{1}{2})^2≥0$, for all $x∈ R)$

$⇒ f(x) > 24$ for all $x ∈ R$.

Therefore, the minimum value of f(x) is 24, it has no maximum value.