若x^2+y^2=0,则x=y=0是真命题吗?它没说x,y属于R,需不需要考虑虚数?比如x=i,y=1?

若3x-5y=0,则x+y/x=（）,x-y/y=（）,2x-3y/2x+3y=( ) 若(x*x+y*y)(x*x+y*y)-4x*x*y*y=0,求代数式(x*x+5xy+y*y)/(x*x+2xy+y*y)的值 已知x*x+4x+y*y-2y+5=0,则x*x+y*y=? 若x-y不等于0,2x-3y=0,则分式(10x-11y)/(x-y)的值是（）?(10x-11y)/(x-y) =[(8x-8y)+(2x-3y)]/(x-y) =8为什么8X-8Y=8？(10x-11y)/(x-y)=[(8x-8y)+(2x-3y)]/(x-y)=8+(2x-3y)]/(x-y)=8+0=8 (5)若x/2=y/3(y不为0）则x/y=____,x+y/y=___,y/x-y=___. 若x+y=1,x不等于0则x+(2xy+y^2)/x/(x+y)/x= 若2x-5y=0,则y：x x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 若x,y满足|2x-y-3|+|3x+2y+1|=0,则x= y= 若x,y满足|x-y+1|+(x+y+3)^2=0则x^2-y^2= 若线段x ,y 满足[2x-3y]*[3x+2y]=0 则x/y=? 若x^2+y^2-6x+8y+25=0 则y/x-x/y的值是 若实数x y满足（x+y)²+（x+y)-2=0则x+y值为 若x^2+y^2+2x-2y+2=0则x+y=? 若|x+y-3|+(x-y-5)^2=0,则x)^2-y^2= 若|x|=2,|y|=3,且y/2+x《0则x+y 若|x+y+1|+(x-2y)的平方=0,则x+2y=? 若实数x,y满足x^2-xy-y^2 =0,则x/y=?