Question

the following
factorise Using identity

(4). 25x² - 40 xy +16y²​

Answer 1

$25 {x}^{2} - 40xy + 16 {y}^{2} \\ = {(5x)}^{2} - 2 \times 5x \times 4y + {(4y)}^{2} \\ = { \:(5x - 4y)}^{2} \\ = (5x - 4y)(5x - 4y)$