化简下列各式:(1)5ab﹣3ab+12ab;(2)4x2y﹣2xy2﹣5xy2+2x2y;(3)2(x2y+xy)﹣3(x2y﹣xy)﹣4x2y;(4)a2﹣
题型:解答题难度:一般来源:期中题
化简下列各式: (1)5ab﹣3ab+12ab; (2)4x2y﹣2xy2﹣5xy2+2x2y; (3)2(x2y+xy)﹣3(x2y﹣xy)﹣4x2y; (4)a2﹣2[a2﹣(2a2﹣b)]. |
答案
解:(1)5ab﹣3ab+12ab =(5﹣3+12)ab =14ab; (2)4x2y﹣2xy2﹣5xy2+2x2y =(﹣2﹣5)xy2+(4+2)x2y =﹣7xy2+6x2y; (3)2(x2y+xy)﹣3(x2y﹣xy)﹣4x2y =2x2y+2xy﹣3x2y+3xy﹣4x2y =5x2y+5xy; (4)a2﹣2[a2﹣(2a2﹣b)] =a2﹣2[a2﹣2a2+b)] =a2﹣2a2+4a2﹣2b =3a2﹣2b. |
举一反三
有这样一道计算题:“计算(2x3﹣3x2y﹣2xy2)﹣(x3﹣2xy2+y3)+(﹣x3+3x2y﹣y3)的值,其中x=,y=﹣1”,甲同学把x=看错成x=﹣,但计算结果仍正确,亲爱的同学,你能解释是怎么一回事吗? |
下列运算正确的是 |
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A.﹣a2b+2a2b=a2b B.2a﹣a=2 C.3a2+2a2=5a4 D.2a+b=2ab |
下列计算正确的是 |
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A.3a+2b=5ab B.5y﹣3y=2 C.7a+a=7a2 D.3x2y﹣2yx2=x2y |
化简:﹣2a+(2a﹣1)的结果是 |
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A.﹣4a﹣1 B.4a﹣1 C.1 D.﹣1 |
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