Question

Factorise (1 - a^2) (1 - b^2) + 4ab
​

Answer 1

$(1 - {a}^{2} )(1 - b {}^{2} ) + 4ab \\ = 1 + (ab) {}^{2} - a {}^{2} - {b}^{2} + 4ab \\ = 1 + (ab) {}^{2} - (a {}^{2} + {b}^{2} - 2ab) + 2ab \\ = 1 +( ab) {}^{2} + 2ab \: - (a - b) {}^{2} \\ = 1 + ab(ab + 2) - (a - b) {}^{2}$

Answer 2

Refer to the attached image ❤