If $x = -1$ and $x = -2$ are the extreme points of $f(x) = a\log|x| + βx^2 +x$ then |
$α=\frac{-2}{3},β=\frac{1}{6}$ $α=-\frac{2}{3},β=-\frac{1}{6}$ $α=\frac{2}{3},β=\frac{1}{6}$ $α=\frac{2}{3},β=-\frac{1}{6}$ |
$α=\frac{2}{3},β=\frac{1}{6}$ |
The correct answer is Option (3) → $α=\frac{2}{3},β=\frac{1}{6}$ Given: $f(x)=a\log|x|+\beta x^{2}+x$ Extreme points occur where $f'(x)=0$. Differentiate: $f'(x)=a\frac{1}{x}+2\beta x+1$ Given that $x=-1$ and $x=-2$ are extreme points, so: $a\frac{1}{-1}+2\beta(-1)+1=0$ $-a-2\beta+1=0$ (1) $a+2\beta=1$ Next condition: $a\frac{1}{-2}+2\beta(-2)+1=0$ $-\frac{a}{2}-4\beta+1=0$ (2) $\frac{a}{2}+4\beta=1$ Multiply (1) by 1 and (2) by 1 to solve: (1) $a+2\beta=1$ (2) $\frac{a}{2}+4\beta=1$ Multiply (2) by 2: $a+8\beta=2$ Subtract (1) from this: $a+8\beta - (a+2\beta)=2-1$ $6\beta=1$ $\beta=\frac{1}{6}$ Substitute into (1): $a+2\left(\frac{1}{6}\right)=1$ $a+\frac{1}{3}=1$ $a=\frac{2}{3}$ The required values are: $a=\frac{2}{3}$ and $\beta=\frac{1}{6}$ |