Question

Find all of the values of x where the tangent line is horizontal.
f(x)= 2x^3+39x^2+252x+14

Answer 1

Set the derivative of f(x) to zero\[6 x^2+78 x+252=0 \]and solve for x:\[6 (x+6) (x+7)=0\]x=-6, x=-7

Answer 2

thank you:)