Question

factorise : 25(2x - y)² - 16(x - 2y)² 

Answer 1

25(2x - y)² - 16(x - 2y)²

= (5 (2x - y))² - (4 (x - 2y))²

= [5(2x - y) - 4 (x - 2y)][5(2x - y) + 4(x - 2y)]

= [10x - 5y - 4x + 8y][10x - 5y + 4x - 8y]
                                   ....[a² - b² = (a - b)(a + b)]

= (6x + 3y)(14x - 13y)

= 3(2x + y)(14x - 13y)