Suppose y = 2x + 1 , where x and y are functions of t.

Question

Suppose y =

2x + 1

,

 where x and y are functions of t.

(a) If dx/dt = 15,

 find dy/dt

 when x = 4.

(b) If dy/dt = 2,

 find dx/dt

 when x = 40.

dx

dt

 =

Answer 1

y = √(2x+1)

dy/dt = (1/2)(1/√(2x+1))(2)dx/dt = (1/√(2x+1))dx/dt

a) if dx/dt = 15 and x = 4

dy/dt = (1/√(8+1))(15) = 15/3 = 5

b) if dy/dt = 2 and x = 40

2 = (1/√(80+1))dx/dt

dx/dt = 2(9) = 18