问题
解答题
已知y2-5y=20,求(y-1)(2y-1)-(y+1)2+1的值.
答案
∵y2-5y=20,
∴(y-1)(2y-1)-(y+1)2+1,
=2y2-3y+1-y2-2y-1+1,
=y2-5y+1,
=20+1,
=21.
已知y2-5y=20,求(y-1)(2y-1)-(y+1)2+1的值.
∵y2-5y=20,
∴(y-1)(2y-1)-(y+1)2+1,
=2y2-3y+1-y2-2y-1+1,
=y2-5y+1,
=20+1,
=21.