(1)-(2)得
x^2=y^2
(1)x=y
x^2+2x^2-10x=0
3x^2-10x=0
x(3x-10)=0
x1=0 x2=10/3
y1=0 y2=10/3
(2)x=-y
x^2-2x^2+10x=0
-x^2+10x=0
x(-x+10)=0
x3=10
y3=-10
所以共有3組解 (0,0)(10/3,10/3)(10,-10)你再算算 這個方程有四個解若x=-10y=10 代入得100-200+100=0 成立及100-200-100=-200不成立所以只有3個解。我題目打錯了，應該是x平方+2xy-10x=0 y平方+2xy-10y=0(1)-(2) x^2-y^2 -10x+10y=0(x-y)(x+y) -10(x-y)=0(x-y)(x+y-10)=0得x=y 或x+y=10(1)x=y x^2+2x^2-10x=0 3x^2-10x=0 x1=0 x2=10/3y1=0y2=10/3(2)x+y=10 y=10-xx^2+2x(10-x)-10x=0x^2+20x -2x^2-10x=0-x^2+10x=0x3=0x4=10y3=10y4=10-10=0所以共有(0,0)(10/3,10/3)(10,0)(0,10)4個解