Practicing Success
If $f(x) = x, x ≤ 1$ and $f(x) = x^2+bx+c,x>1$ and $f'(x)$ exists finitely for all $x∈R$, then |
$b=-1,c∈R$ $c=1,b∈R$ $b=1,c=-1$ $b=-1,c=1$ |
$b=-1,c=1$ |
f(x) is differentiable at x = 1 $∴\underset{h→0}{\lim}\frac{f(1+h)-f(1)}{h}=\underset{h→0}{\lim}\frac{f(1-h)-f(1)}{-h}$ Now, $\underset{h→0}{\lim}\frac{f(1+h)-f(1)}{h}=\underset{h→0}{\lim}\frac{(1+h)^2+b(1+h)+c-1}{h}$ $=\underset{h→0}{\lim}\frac{h^2+(2+b)h+b+c}{h}$ $\underset{h→0}{\lim}\frac{f(1-h)-f(1)}{-h}=\underset{h→0}{\lim}\frac{1-h-1}{-h}=1$ The two limits can be equal if 2 + b =1, b + c = 0 |