(1)化简(4x2-2x-1)-{5x2-[8x-2-3(x2+x)]-x2}

1个回答

  • 解题思路:(1)对同类项合并进行化简.

    (2)先合并同类项化成最简式,然后求解.

    (3)根据已知方程得到x,y的值.然后通过合并同类项将整式化简成最简式代入x,y的值求解.

    (1)原式=4x2-2x-1-{5x2-[8x-2-3x2-3x]-x2}=4x2-2x-1-{5x2-8x+2+3x2+3x-x2}=4x2-2x-1-5x2+8x-2-3x2-3x+x2=-3x2+3x-3

    (2)原式=5abc-{2a2b-[3abc-4ab2+a2b]}+3ab2=5abc-{2a2b-3abc+4ab2-a2b}+3ab2=5abc-2a2b+3abc-4ab2+a2b+3ab2=8abc-a2b-ab2;将a,b,c的值代入得:原式=[8/3]

    (3)根据题意得,(x-2)2+|xy-4|=0则,(x-2)2=0,|xy-4|=0解得:x=2,y=2

    原式=3x2y+{-2x2y-[-2xy+(x2y-4x2)-xy]+xy2}=3x2y+{-2x2y-[-2xy+x2y-4x2-xy]+xy2}=3x2y+{-2x2y+2xy-x2y+4x2+xy+xy2}=3x2y-2x2y+2xy-x2y+4x2+xy+xy2=4x2+3xy+xy2
    将x=2,y=2代入得:原式=36

    点评:

    本题考点: 整式的加减—化简求值;非负数的性质:绝对值;非负数的性质:偶次方.

    考点点评: 对整式的化简首先去括号,同时含有小括号,中括号,大括号的从里往外一层一层去括号.在去括号时应注意去掉括号后单项式应变换符合.去完括号对整式进行合并同类项来化简.