Find the slope of tangent of the curve `y =4x` at the point `(-1,4)`.

Options

A. `-6`
B. `6`
C. `-8`
D. `8`

Answer

C

Explanation

Let f(x)=`4x^(2)`
`therefore f'(-1)=underset(hrarr0)"lim"(f(-1+h)-f(-1))/(h)`
`=underset(hrarr0)"lim"(4(1-2h+h^(2))-4)/(h)`
`=underset(hrarr0)"lim"4(-2+h)=4(-2)`
=- 8
`f'( -1)=-8` is the slope of tangent at point (-1,4) of the curve `y=4x^(2)`.