MY NOTES PRACTICE ANOTHER Find an equation for the line tangent to the curve y = (Vx + 9)(x3 - 8) at x = 1. 1= 68x - 140 X [0.5/1 Points] DETAILS PREVIOUS ANSWERS MY NOTES Consider the function f(x) = - x - 2 x2 + 21 Determine the number of points on the graph of y = f(x) that have a horizontal tangent line. In other words, determine the number of solutions to f'(x) = 0. Determine the values of x at which f(x) has a horizontal tangent line. Enter your answer as a comma-separated list of values. The order of the values does not matter. Enter DNE if f(x) does not have any horizontal tangent lines. 1 1 6' 14 X