Let $f(x) = 4x^3- 18x^2 +27x - 5,x∈R$. Then which of the following statements are TRUE? (A) $f''(x) = 24x - 36$ Choose the correct answer from the options given below: |
(A) and (B) only (A) and (C) only (B) and (C) only (A) and (D) only |
(A) and (C) only |
The correct answer is Option (2) → (A) and (C) only $f(x)=4x^{3}-18x^{2}+27x-5$ $f'(x)=12x^{2}-36x+27=12\left(x-\frac{3}{2}\right)^{2}\ge 0$ $f''(x)=24x-36$ Critical point: $f'(x)=0 \Rightarrow x=\frac{3}{2}$ and $f''\!\left(\frac{3}{2}\right)=0$. Since $f'(x)\ge 0$ for all $x$ and vanishes only at $x=\frac{3}{2}$, $f$ is strictly increasing with a stationary inflection; no local extrema. True statements: (A) and (C) |