factoring polynomials/algebra problem?

Question

this problem is under the chapter in my textbook "factoring by grouping/gcf"

solve for the indicated variable:

b^2x^2 + a^2 y^2 = a^2b^2 for a^2

Answer 1

b²x² + a²y² = a²b²
b²x² = a²b² - a²y²
b²x² = a²(b² - y²)
b²x² / (b² - y²) = a²