Answer:
(a+b)(a-b)-19
Step-by-step explanation:
a²-b²
=a²-ab+ab-b²
=a(a-b)+b(a-b)
=(a+b)(a-b)
it'll be more easy to understand if u try solving it the other way(from bottom to the top)
there fore... a²-b²=(a+b)(a-b)
and -20+1=-19
so then the ans will be(a+b)(a-b)-19
