Chapter 9 - Solving Quadratic Equations - 9.5 - Solving Quadratic Equations Using the Quadratic Formula - Exercises - Page 521: 4

$a=1, b=-4$ and $c=12$

Given : $x^{2}-4x=-12$ Adding $12$ on both sides, we obtain $x^{2}-4x+12=-12+12$ This can be written as $x^{2}-4x+12=0$ Comparing $x^{2}-4x+12=0$ with $ax^{2}+bx+c$, we get $a=1, b=-4$ and $c=12$