Question

Find the derivative of f(x) = 11x2 + 5x at x = 9.

Answer 1

Answer: 203

Step-by-step explanation:

The given function : $f(x) = 11x^2 + 5x$

Now, we differentiate the given function with respect to x on the both sides , we get

 $f'(x) = (2)11x + 5$    [Since $(x^n)'=nx^{n-1}$ ]

$\Rightarrow\ f'(x)=22x+5$

Substitute x = 9 , we get

$\Rightarrow\ f'(9)=22(9)+5\\\\\Rightarrow\ f'(9)=198+5\\\\\Rightarrow\ f'(9)=203$

Hence, the derivative of the given function at x= 9 is 203.

Answer 2

F(x) = 11x² + 5x 

f'(x) = 22x + 5

Hence,

f'(9) = (22 * 9) + 5 = 198 + 5 = 203