化简下列各式:(1)-(x+y)+(3x-7y);                 (2)(4a2-3b2)-[2(a2-1)+2b2-3]

问题描述:

化简下列各式:
(1)-(x+y)+(3x-7y);                 (2)(4a2-3b2)-[2(a2-1)+2b2-3]

(1)原式=-x-y+3x-7y,
=2x-8y;
(2)原式=4a2-3b2-[2a2-2+2b2-3],
=4a2-3b2-2a2+2-2b2+3,
=2a2-5b2+5.
答案解析:(1)运用整式的加减运算顺序,先去括号,再合并同类项.
(2)运用整式的加减运算顺序,先去小括号,后去中括号,再合并同类项.
考试点:整式的加减.
知识点:本题考查了整式的加减,属于基础题,注意细心运算.