X and Y variables

Question

Use the given information to find the unknown value.

y varies directly as the cube of x. When x=3, then y=5. Find y when x=4. 

Enter the exact answer.

Answer 1

y= kx^(1/3)

5 = k(3^(1/3))

k=5/(3^(1/3))

y = (5/(3^(1/3))(4)

y = 20/3^(1/3)= about 13.87

y = exactly (20/3)(3^(2/3)

y = exactly , 20/3 times the cube root of 9 when x=3

y= about 14 when x=3