Step-by-step explanation:
the derivative of an inverse function is
1/f'(f^-1(x))
f'(x) = -6x²
f^-1(7) is solving the original function equation for x under the knowledge that y = 7
7 = 5 - 2x³
2 = -2x³
-1 = x³
=>
x = -1
f'(-1) = -6×(-1)² = -6×1 = -6
so,
(f^-1)'(7) = -1/6
