Find the difference. k k2 − 9k + 20 − 5 k2 − 9k + 20

This is the concept of algebra, to get the difference of the expression given we proceed as follows;
(k^2-9k+20)-(k^2-9k+20)
collecting like terms we get:
(k^2-5k^2)+(-9k-9k)+(20-20)
=-4k^2-18k+0
=-4k^2-18k
The answer is (-4k^2-18k)