Mark M. answered 11/04/18
Retired math prof. Calc 1, 2 and AP Calculus tutoring experience.
Slope of tangent to the curve y = xf(x2) when x = 1 is dy/dx evaluated at x = 1.
By the Product Rule and Chain Rule, dy/dx = f(x2) + xf'(x2)(2x)
So, when x = 1, dy/dx = f(1) + 2f'(1)
The tangent line to the curve y = xf(x2) when x = 1 has equation 2y + 3x = 6, which can also be written as y = (-3/2)x + 3.
So, f(1) + 2f'(1) = -3/2.
Also, when x = 1, y = (-3/2)(1) + 3 = 3/2. The point (1, 3/2) is the point of tangency. So, f(1) = 3/2.
Therefore, 3/2 + 2f'(1) = -3/2
2f'(1) = -3
f'(1) = -3/2