### Home > PC3 > Chapter 7 > Lesson 7.2.5 > Problem7-131

7-131.

Given $x^2+y^2=1$, rewrite each of the expressions below in terms of only $x$.

1. $\frac { y ^ { 2 } } { x } + x$

$\frac{y^2}{x}+\frac{x^2}{x}$

1. $\frac{y^2}{\frac{1}{x^2}-1}$

$\frac{\frac{y^2}{1}}{\frac{1}{x^2}-\frac{1}{1}}\cdot\frac{\frac{x^2}{1}}{\frac{x^2}{1}}$

$1-x^2=y^2$

1. $\frac { 1 } { 1 - y } + \frac { 1 } { 1 + y }$

$\frac{1+y}{(1-y)(1+y)}+\frac{1-y}{(1-y)(1+y)}$

$1-y^2=x^2$

1. $\frac{1}{\frac{1}{x}-\frac{y}{x}}+\frac{1}{\frac{1}{x}+\frac{y}{x}}$

$\small \frac{1}{\frac{1-y}{x}}+\frac{1}{\frac{1+y}{x}}$

$\frac{x}{1-y}+\frac{x}{1+y}$