f'(y) = 4 \cdot \frac(1)(y^2) - (1 + y)(2y)y^4 = 4 \cdot \fracy^2 - 2y(1 + y)y^4 = 4 \cdot \fracy^2 - 2y - 2y^2y^4 = 4 \cdot \frac-y^2 - 2yy^4 = -4 \cdot \ - Abu Waleed Tea