Chapter 8 - Polynomials and Factoring - 8-5 Factoring x2+bx+c - Practice and Problem-Solving Exercises - Page 517: 51

(k-21)(k+3)

You are given $k^{2}$-18k-63. Factor it out: $k^{2}$-21k+3k-63 -break out the b value- ($k^{2}$-21k)+(3k-63) -group the first two and last two terms- k(k-21)+3(k-21) -Find the GCF of each grouping- (k+3)(k-21) -factor out the common term- =(k+3)(k-21)