先化简,再求值:2x2+y2+(2y2-3x2)-2(y2-2x2),其中x=-1,y=2.
先化简再求值:-(x2+y2)+[-3xy-(x2-y2)],其中x=-1,y=2.
先化简,再求值:2x2+(-x2-2xy+2y2)-3(x2-xy+2y2),其中x=2,y=-12
先化简,再求值:(1)2x2-5x x2 4x,其中x=-3 (2)(3x2-xy-2y2)-2(x2 xy-2y2),
先化简再求值2(x2-xy)-3(2x2-3xy)-2[x2-(2x2-xy+y2)],其中x=-1,y=-2.
已知实数x.y满足(x2+y2)(x2+y2-1)=2,求x2+y2的值
化简求值(2X2-2y2)-3(X2y2+X2)+3(X2y2+y2),其中X=-1,y=2
先化简,再求值:(-3xy)2(x2+xy-y2)-3x2y2(3x2+3xy+y2),其中x=-43
已知x,y为实数,且(x2 +y2)(x2 +y2+2)=3.求x2 +y2的值
已知2x=3y,求xy/(x2+y2)-y2/(x2-y2)的值
已知2x+y=7,x2+y2=5,求(4x+2y)2-3x2-y2+2(1-y2)的值.
已知实数x、y满足(x2+y2)(x2+y2-1)=2,则x2+y2的值为______.
先化简再求值:y(x+y)+(x-y)2-x2-2y2,其中x=-13