(x+y)^2=18,(x-y)^2=6,分别求x^2+y^2及x^2+3xy+y^2的值
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(x+y)^2=18,(x-y)^2=6,分别求x^2+y^2及x^2+3xy+y^2的值(x+y)^2=18,(x-y)^2=6,分别求x^2+y^2及x^2+3xy+y^2的值(x+y)^2=18
(x+y)^2=18,(x-y)^2=6,分别求x^2+y^2及x^2+3xy+y^2的值
(x+y)^2=18,(x-y)^2=6,分别求x^2+y^2及x^2+3xy+y^2的值
(x+y)^2=18,(x-y)^2=6,分别求x^2+y^2及x^2+3xy+y^2的值
(x+y)^2=18=x^2+y^2+2xy,(x-y)^2=x^2+y^2-2xy=6
得出xy=3
x^2+y^2=(x+y)^2-2xy=18-6=12
x^2+3xy+y^2==(x+y)^2+xy=18+3=21
x^2+y^2＝12
x^2+3xy+y^2=21
x^2+y^2=[(x+y)^2+(x-y)^2]/2=(18+6)/2=12
x^2+3xy+y^2=(x+y)^2+xy=(x+y)^2+[(x+y)^2-(x-y)^2]/4=18+(18-6)/4=21
x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2
【2(x-y)^3-8(x-y)^2(x+y)+6y(x-y)^2】/2(x-y)^2=
x+y/2+x-y/6=5 2(x+y)-3(x-y)=-2
（x+y）/2- x-y/2=6 3(x+y)=4(x-y)
x+y/3+x-y/2=6 4(x+y)-2(x-y)=40
[(2x-y)(2x+y)+y(y-6x)]÷2x=?
2(x+y)-3(x-y)=1 6(x+y)+(x-y)=51
{3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1
{6(x-y)-7(x+y)=21 {2(x-y)-5(x+y)=-1
6(x-y)-2(x+y)=14 3(x-y)+(x+y)=5
x+y/2+x-y/3=6,4(x+y)-3(x-y)=-20
{(x+y)/2+(x-y)/3=6 4(x+y)-3(x-y)=-20
4(x+y)-3(x-y)=-20,2/x+y+3/x-y=6
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