Применим формулу сокращённого умножения:
a² - b² = (a - b)·(a + b).
1) 9·x²-4·y²-3·x+2·y = (3·x)²-(2·y)²-(3·x-2·y) = (3·x-2·y)·(3·x+2·y) - (3·x-2·y) =
= (3·x-2·y)·(3·x+2·y-1);
2) 81 - (3-8·y)² = 9² - (3-8·y)² = (9-(3-8·y))·(9+(3-8·y)) = (9-3+8·y)·(9+3-8·y) =
= (6+8·y)·(12-8·y) = 2·(3+4·y)·4·(3-2·y) = 8·(3+4·y)·(3-2·y);
3) 36-(y+1)² = 6²-(y+1)² = (6-(y+1))·(6+(y+1)) = (6-y-1)·(6+y+1) = (5-y)·(7+y);
4) (4-5·x)²-64 = (4-5·x)²-8² = (4-5·x-8)·(4-5·x+8) = (-4-5·x)·(12-5·x) =
= -(4+5·x)·(12-5·x) = (4+5·x)·(5·x-12).
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Объяснение: