## Introductory Algebra for College Students (7th Edition)

Use the Pythagorean Theorem. Let x be the height the ladder reaches. $20^2=15^2+x^2$ Simplify. $400=225+x^2$ Subtract 225 from each side. $400-225=225+x^2-225$ Simplify. $175=x^2$ Take the square root of each side. $\sqrt{175}=\sqrt{x^2}$ Simplify and round. $13.2\approx x$