## Algebra 2 Common Core

$$b=15$$
Use the Pythagorean Theorem: $$c^{2}=a^{2}+b^{2}.$$ Rearrange terms: $$b^{2}=c^{2}-a^{2}.$$ Substitute in $a=8$ and $c=17:$ $$b^{2}=17^{2}-8^{2}=289-64=225.$$ Take the square root of both sides: $$\sqrt {b^{2}}=\sqrt {225}$$ $$b=15.$$