解方程组3(x y)-4(x-y)=-9

由方程1得：x=2y-3代入方程2得：(2y-3)^2+y(2y-3)+4y^2-19=0整理得：10y^2-15y-10=05(2y^2-3y-2)=05(2y+1)(y-2)=0解得：y=-1/2

y=3x^2-8,代入第2个方程得：x^2+x(3x^2-8)+3x^2-8=43x^3+4x^2-8x-12=0解得只有一个实根：x=1.67758093466546故y=0.442833377再问

3x^2-y^2=8（1）x^2+xy+y^2=4（2）将2*(2)有2x^2+2xy+2y^2=8,与(1)连等2x^2+2xy+2y^2=3x^2-y^2,移项有x^2-2xy-3y^2=0用十字

一式子减去二式子乘以2的差得x²-2xy-3y²=0(x+y)(x-3y)=0x=-y或x=3y当x=-y时代入一式3y²-y²=8y=±2当x=3y时代入一式

xy/(2x+y)-xy/(2x-y)=3xy/(2x-y)+xy/(2x+y)=4；一、两公式对加得2xy/(2x+y)=7xy=(2x+y)*7/2二、把xy代入原公式求解就行了：(2x+y)*7

解1式：(x+4y)(x-y)=0x=-4y时,解2式得：x=-10/3,y=5/6;x=10/3,y=-5/6x=y时,解2式得：x=5,y=5;x=-5,y=-5

另x=3/y,带入则y2=1或y2=9/4,y=1,x=3,y=-1,x=-3,y=3/2,x=2,y=-3/2,x=-2

x^2+xy+2y^2=9+y2x^2+2xy+4y^2=18+2y2x^2+2xy+4y^2+x=1918+2y+x=19x+2y=1x=1-2y(1-2y)^2+(1-2y)y+2y^2-y=94

x+2y=3m+53x-4y=4m-15第一个式子乘以2加第二个式子得：5x=10m-5x=2m-1再代入x+2y=3m+5得y=m/2+3所以x=2m-1y=m/2+3

(x²+y²)(x²-y²)=15xy(x²-y²()-=6相除2x²+2y²=5xy(x-2y)(2x-y)=0x=2

一式子减去二式子乘以2的差得x²-2xy-3y²=0(x+y)(x-3y)=0x=-y或x=3y当x=-y时代入一式3y²-y²=8y=±2当x=3y时代入一式

(1)×7+(2)×328y+27y=55xy所以y=0或x=1分别代入所以x=0.y=0x=1,y=1/2

两式相加得x=4+xy即x=4/(1-y)①两式相减得y=-1-4xy②①代入②y=-1-4y*4/(1-y)整理得y²-16y-1=0解得y=8±√65代入①,即可算出x了如有不明白,可以

x+y=-3x=-3-y带入xy=2(-3-y)y=2-y^2-3y-2=0y^2+3y+2=0(y+1)(y+2)=0y1=-1y2=-2x1=-2x2=-1

x=2,y=0.5

即(x+y)²=9(x-y-3)(x-y-1)=0所以x+y=3,x-y=1x+y=3,x-y=3x+y=-3,x-y=1x+y=-3,x-y=3所以x=2,y=1x=3,y=0x=-1,y

因为：xy=(x-10)(y+1)→xy=xy+x-10y-10①xy=(x-15)(y+3)→xy=+3x-15y-45②由①、②得：x=10y+10③x=5y+15④将③‐­④得：10y+

由(x-2)(y+3)=xy(x-5)(y+2)=xy得3x-2y-6=02x-5y-10=0上面方程化为6x-4y-12=06x-15y-30=0两式相减得11y=-18,y=-18/11,代入任意

x1=-1/12*(1261+234*29^(1/2))^(1/3)-13/12/(1261+234*29^(1/2))^(1/3)+5/12x2=1/24*(1261+234*29^(1/2))^(

4x-3y=k①2x+3y=5②①-②×2得:4x-3y-4x-6y=k-10-9y=k-10y=-(k-10)/9①+②得:4x-3y+2x+3y=k+56x=k+5x=(k+5)/6因为x