题目内容
【题目】计算:
(1)3(x2﹣5xy)﹣4(x2+2xy﹣y2)﹣5(y2﹣3xy)
(2)(x﹣x2+1)﹣2(x2﹣1+3x)
【答案】(1)﹣x2﹣8xy﹣y2;(2)﹣3x2﹣5x+3.
【解析】
(1)先去括号,然后合并同类项即可;
(2)按照去括号,合并同类项的法则进行化简即可.
解:(1)3(x2﹣5xy)﹣4(x2+2xy﹣y2)﹣5(y2﹣3xy)
=3x2﹣15xy﹣4x2﹣8xy+4y2﹣5y2+15xy
=﹣x2﹣8xy﹣y2;
(2)(x﹣x2+1)﹣2(x2﹣1+3x)
=x﹣x2+1﹣2x2+2﹣6x
=﹣3x2﹣5x+3.
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