Question

If y = 2x3 – 4x and dx, dt equals 4, find dy, dt when x = 1. give only the numerical answer. for example, if dy, dt = 3, type only 3.

Answer 1

y= 2*3-4x;
    differentiate with respect to t we get dy = -4xdt; -- eqn 1
   given dt = 4 substitute in eqn 1 we get , dy =-4 x( 4) = -16x; --eqn2
  given x=1 then sub then the value of x in eqn 2 we get dy = -16(1)=-16
   ie Ans dy = -16