Answer:
7^2+2ab - 4b^2
Step-by-step explanation:
A² + b² = 7b
b² + (2b-a) ²= 7²
FOIL
b^2 +4b^2-4ba+a^2= 7^2
Rewriting
a^2 -2ab + b^2 +4b^2 -2ab = 7^2
Add 2ab and subtract 4b^2 from each side
a^2 -2ab + b^2 +4b^2 - 4b^2 -2ab+2ab = 7^2+2ab - 4b^2
a^2 -2ab + b^2 = 7^2+2ab - 4b^2
(a-b)^2 = 7^2+2ab - 4b^2
