find f(x) = x(3x-1)

Question

i need to find f'(x) at the given x value.

f(x)=x(3x-1) ; x=1  means f'(1)

Answer 1

Remember the formula d/dx uv = u dv/dx+ v du/dx

Given function f(x) = x(3x-1)

Apply derivatiive to each side with respect of x.

d/dx(f(x)) = d/dx[x(3x-1)]

f'(x) = xd/dx(3x-1)+(3x-1)d/dx(x)

= x(3)+(3x-1)1

= 3x+3x-1

= 6x-1

Now f'(1) = 6*1-1

= 6-1 = 5