七年期数学课课精练的一道题已知m,x,y满足条件①5/2(x-2)^2+3/4|m|=0,②-2a^2b^y+1与3a^2b^3是同类项,求代数式0.375x^2y+5m^2x-｛-7/16x^2y+[-1/4xy^2+(-3/16x^2y-3.475xy^2)]-6.275xy^2｝
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七年期数学课课精练的一道题
已知m,x,y满足条件①5/2(x-2)^2+3/4|m|=0,②-2a^2b^y+1与3a^2b^3是同类项,求代数式0.375x^2y+5m^2x-｛-7/16x^2y+[-1/4xy^2+(-3/16x^2y-3.475xy^2)]-6.275xy^2｝
李军怀回答：
5/2(x-2)^2+3/4|m|=0
绝对值和平方大于等于0,相加等于0
所以都等于0
x-2=0,x=2,m=0
-2a^2b^y+1与3a^2b^3是同类项
所以b的系数相等
所以y+1=3,y=2
0.375x^2y+5m^2x-｛-7/16x^2y+[-¼xy^2+(-3/16x^2y-3.475xy^2)]-6.275xy^2｝
先把m=0代入
=0.375x^2y-｛-7/16x^2y+[-¼xy^2+(-3/16x^2y-3.475xy^2)]-6.275xy^2｝
=0.375x^2y-｛-7/16x^2y+[-3/16x^2y-3.725xy^2]-6.275xy^2｝
=0.375x^2y-(-0.625x^2y-3.725xy^2-6.275xy^2)
=0.375x^2y+0.625x^2y+3.725xy^2+6.275xy^2
=x^2y+10xy^2
=8+10*8
=88
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