Вправи: 102

102. Спростіть вираз:

1) y2y3-81 – yy+9 = y2(y-9)(y+9) – y\y-9y+9 = y2-y(y-9)(y-9)(y+9) = y2-y2+9y(y-9)(y+9) = 9yy2-81;

2) nn-7 – n2n2-14n+49 = n\n-7n-7 – n2(n-7)2 = nn-7-n2 (n-7)2 = n2-7n-n2 (n-7)2 = –7n(n-7)2.