Question

81a square -25b square
Explanation?

Answer 1

$81 {a}^{2} = 9 \times 9 \times a \times a = (9a) {}^{2}$

$25 {b}^{2} = 5 \times 5 \times b \times b = (5b) {}^{2}$

$(9a) {}^{2} - (5b {)}^{2}$

It is now in the form of identity,

$a {}^{2} - b {}^{2} = (a + b) \times (a - b)$

therefore,

${(9a)}^{2} - (5b {)}^{2} = (9a + 5b) \times (9a - 5b)$