Question

LAST ONE!! y is directly proportional to the square of x. Given that y=32 when x=4, find the value of x when y=18

Answer 1

±3

Explanation:

y is directly proportional to the square of x.

`y \propto x^(2)`

`y = kx^(2)`

Find the value of k constant when y=32 and x=4.

`32=k(4)^2`

Square the number 4.

`32=16k`

Divide both sides with 16.

`32/16=k`

`k=2`

The value of k constant is 2.

Find the value of x when y=18

`y=2x^2`

`18=2x^2`

`18/2=x^2`

`9=x^2`

`x= \± √(9)`

`x=\± 3`

The value of x when y = 18 is ±3.