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

Answer:

±3

Step-by-step 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

$y=2x^2$

$18=2x^2$

$18/2=x^2$

$9=x^2$

$x= \± \sqrt{9}$

$x=\± 3$

The value of x when y = 18 is ±3.