If y^3 = 16x^2

Determine dx/dt
When x= 4 and dy/dt= -1

y^3 = 16x^2

when x = 4
y^3 = 16(256)
y = 16

3y^2 dy/dt = 32x dx/dt
sub in our values
3(256) (-1) = 32(4) dx/dt
dx/dt = -768/128
= -6