Question

use the formula : a square -b square =(a+b) (a-b) to find the factore of (81x square-64y square)

Answer 1

81x²- 64y²
= (9x)²- (8y)²
=(9x-8y) (9x+8y)

Answer 2

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

$(81^{2} - 64 {}^{2} ) = (81 + 64) \times (81 - 64) \\ (81^{2} - 64 {}^{2} ) = (145) \times (13) \\ (81^{2} - 64 {}^{2}) = 145 \times 13 \\ (81^{2} - 64 {}^{2}) = 1885$