若x²+xy+y²=14,x²-xy+y²=28,求x+y的值

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若x²+xy+y²=14,x²-xy+y²=28,求x+y的值若x²+xy+y²=14,x²-xy+y²=28,求x+y

若x²+xy+y²=14,x²-xy+y²=28,求x+y的值
若x²+xy+y²=14,x²-xy+y²=28,求x+y的值

若x²+xy+y²=14,x²-xy+y²=28,求x+y的值
x²+xy+y²=14,x²-xy+y²=28
相加
2(x²+y²)=42
x²+y²=21
相减
2xy=-14
所以(x+y)²
=x²+2xy+y²
=7
x+y=±√7

若x²+xy-2y²=0,则x²+3xy+y²/x²+y² 若x² +xy+y² =14,x² -xy+y²=28求x+y的值若x²+xy+y²=14,x²-xy+y²=28,求x+y的值 x²+xy-2y²=0则x²+3xy+y²/x²+y² 若|x+y-5|+(xy-6)²=0,求x²+y²的值. 若x²+y²+4x-10y+29=0,则x²y+xy²= （x²+y²)²-x²y²=(x²+y²)²-(xy)²=(x²+y²+xy)(x²+y²-xy)=(x+y)²(x-y)²-xy+xy=(x+y)²(x-y)² 已知x²y²+x²+y²=10xy-16 求x,y 3x²-y²=8x²＋xy＋y²=4 若(x+y-5)²+(xy-6)²=0,则（x+y)²-2xy的值为? 谢谢高手解答x²-xy=2,-xy+y²=5求x²-2xy+ y²,x²- y² 6x²-xy-15y²=0 求x²-2xy+4y²/2x²-3xy-3y²告诉下 6x²-xy-15y²=0 求2x²-3xy-3y²分之x²-2xy+4y² 若x²+xy=-3,y²+xy=5,则x²+2xy+y²的值为? 已知：x²+xy=3,xy+y²=-2 求：2x²-xy-3y² 已知x² -XY = 2,Y² -XY= 5,求x² - 4x Y+ Y² = 2x² + xY -3Y² = x² 已知x² -XY = 2,Y² -XY= 5,求x² - 4x Y+ Y² = 2x² + xY -3Y² = x² + xY- 2Y² =求x² - 4x Y+ Y² = 若x/y=2,求分式(x²-xy+3y²)/(x²+xy+6y²)的值若x/y=2,求7x²-3xy+2y²/2x²-3xy+7y²的值答案是8/3