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(5x^3-7x^3y+3x^2y)+2x^3-(-7x^3y+3x^2y+7x^3)
=5x^3-7x^3y+3x^2y+2x^3+7x^3y-3x^2y-7x^3
=5x^3+2x^3-7x^3+7x^3y-7x^3y+3x^2y-3x^2y
=(5+2-7)x^3+(7-7)x^3y+(3-3)x^2y
=0*x^3+0*x^3y+0*x^2y
=0
所以(5x^3-7x^3y+3x^2y)+2x^3-(-7x^3y+3x^2y+7x^3)的值与字母x、y的取值无关
1年前
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