### Home > APCALC > Chapter 7 > Lesson 7.1.3 > Problem7-29

7-29.

Greta is trying to solve the equation $x − 3\sqrt { x }= −2$. She decides to simplify the problem by letting $u =\sqrt { x }$.

1. Rewrite Greta’s equation using $u$, then solve for $u$.

$\text{If }u=\sqrt{x},\text{ then }u^{2}=x .$

$x-3\sqrt{x}=-2$

$u^2 - 3u = −2$
Solve for $u$.

If $u = 2$ and $u = 1$, what is $x$?

2. If $x = 5$, what is the value of $u$?

Refer to the given information.