Use the derivative of f(x) = 6x^7 + 7x^6 to determine any points on the graph of f(x) at which the tangent line is horizontal
a. f(x) has no points with a horizontal tangent line
b. (0,0) and (-1,1)
c. (1, 13) and (-1,1)
d. (-1, -24)
e. (6,0)
f(x) = 6x^7 + 7x^6
f'(x) = 42x^6 + 42x^5 set to 0
42x^6 + 42x^5 = 0 factor
42x^5 ( x + 1) = 0
Setting both factors to 0, we have that x = 0 and x = -1
When x = 0, f(x) = 0
When x = -1, f(x) = 1
So.......the points are (0, 0) and ( -1, 1) → " b"
+84 
