Chapter 9 - Solving Quadratic Equations - 9.5 - Solving Quadratic Equations Using the Quadratic Formula - Exercises - Page 521: 11

$x=11$ and $x=-1$

Comparing $x^{2}-10x-11=0$ with $ax^{2}+bx+c=0$, we get $a=1$, $b=-10$ and $c=-11$. The quadratic formula is $x=\frac{-b \pm \sqrt {b^{2}-4ac}}{2a}$ Substituting the values, we get $x=\frac{-(-10) \pm \sqrt {(-10)^{2}-4(1)(-11)}}{(2)(1)}=\frac{10\pm 12}{2}$ The solutions are $x=\frac{10+12}{2}=11$ and $x=\frac{10-12}{2}=-1$