x+y=3
兩邊平方
x^2+y^2+2xy=9
x^2+y^2=9-2xy=9-4=5
x^3+x^2y+xy^2+y^3
=(x^3+y^3)+(x^2y+xy^2)
=(x+y)(x^2-xy+y^2)+xy(x+y)
=3*(5-2)+2*3
=15
已知x+y=3,xy=2,求代數(shù)式x^3+x^2y+xy^2+y^3的值
已知x+y=3,xy=2,求代數(shù)式x^3+x^2y+xy^2+y^3的值
數(shù)學(xué)人氣：849 ℃時(shí)間：2019-10-19 06:03:24
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