1-ый способ.
(y-1)² - (6-x)² = ((y-1) - (6-x)) * ((y-1) + (6-x)) = (y-1-6+x) * (y-1+6-x) =
=(y+x-7) * (y-x+5). <em>Формула: a²-b²=(a-b)(a+b)</em>
2-ой способ.
(y-1)² - (6-x)² = (y² -2y +1) - (36 -12x + x²) = y² -2y +1 -36 +12x -x² =
= y² -x² -2y +12x -35. <em>Формула: (a-b)²=a²-2ab+b²</em>
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У/2-у/8=у/4-1 |:8
4у-у=2у-1
4у-у-2у=-1
у=-1