Simplify
1. (7/9a + 9/7b)^2 - ab
2.(3/4x - 4/8y)^2 + 2xy
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Step-by-step explanation:
1) (7/9a + 9/7b)² - ab
(a + b)² = a² + 2ab + b²
= (7/9a)² + 2(7/9a)(9/7b) + (9/7b)² - ab
= 49/81a² + 2ab + 81/49b² - ab
= 49/81a² + ab + 81/49b²
2) (3/4x - 4/8y)² + 2xy
(a - b)² = a² - 2ab + b²
= (3/4x)² - 2(3/4x)(4/8y) + (4/8y)² +2xy
= 9/16x² - 3/4xy + 16/64y² + 2xy
= 9/16x² - 3/4xy + 8/4xy + 16/64y²
= 9/16x² + 5/4xy + 16/64y²
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