The last question please

Question

For what value of t is the slope of the curve undefined for the graph defined by x = 10 – t2, y = t3 – 12t?

Type your answer in the space below to the nearest whole number. (ex: 4)

Answer 1

Since dy/dx = (dy/dt)/(dx/dt)
dy/dx will be undefined if dx/dt = 0 and dy/dt is not zero.

dy/dx = (3t^2-12)/(-2t)
we must exclude t=0

Answer 2

So you mean the answer is "0"?