Brief Calculus.

Question

The graph of  has two horizontal tangents. One occurs at a negative value of  and the other at a positive value of . What is the negative value of  where a horizontal tangent occurs?

x=

What is the positive value of x where a horizontal tangent occurs?

x=

Answer 1

f'(x) = 6x² + 30x - 84 = 0; x² + 5x - 14 = 0: (x + &)(x - 2)) = 0.

From here x = - 7 (x < 0)

or x = 2 (x > 0)