Question

[（x+3y)²-4x²]÷(x+y）怎么算？很急。

Answer 1

〔（x＋3y）^2－4x^2〕÷（x＋y）
平方差
=（x+3y+2x）(x+3y-2x)/(x+y)
合并
=3(x+y)(3y-x)/(x+y)
=3(3y-x)

Answer 2

[（x+3y)2-4x2]÷(x+y）]
=[x^2+6xy+9y^2-4x^2]/(x+y)
=[-3x^2+6xy+9y^2]/(x+y)
=3*(-x^2+2xy+3y^2)/(x+y)
=3*(x+y)*(-x+3y)/(x+y)
=3*(-x+3y)
=-3x+9y