Answer
(k-21)(k+3)
Work Step by Step
Given the polynomial
$k^{2}$ -18k - 63
*** We break of the middle term into two factors that add to give -18 and multiply to give -63. The two numbers are -21 and +3.
$k^{2}$ -21k +3k - 63
We take the GCD of the first two and the GDC of the last two terms.
k(k-21) +3(k-21)
We take (k-21) and factor it out which gives us.
(k-21)(k+3)
