x+y+xy+54解题思路

谈谭孔1877已知x.y满足x*x+y*y+5/4=2x+y,求代数式xy/x+y的值
余姣印19197679841 ______ x*x+y*y+5/4=2x+y,x*x+y*y+5/4-2x-y=0,x*x-2x+1+y*y-y+1/4=0,所以(x-1)的平方+(y-1/2)的平方=0,得x=1,y=1/2 所以xy/x+y=1/3

谈谭孔1877已知x、y满足x^2+y^2+5/4=2x+y,求代数xy/x+y -
余姣印19197679841 ______ x^+y^+5/4=2x+y, (x^2-2x+1)+(y^2-y+1/4)=0 (x-1)^2+(y-1/2)^2=0 x-1=0 y-1/2=0 x=1,y=1/2 x-2y+2xy=1-1+2*1*1/2=1 祝你学习天天向上,加油!!!!!!!!!

谈谭孔1877X+X+Y+Y+Y=56,X+X+X+Y+Y=54.X=?Y=?XY=? -
余姣印19197679841 ______[答案] 原方程组即为: 2X+3Y=56……① 3X+2Y=54……② ①+②,得 5X+5Y=110 即:X+Y=22,两边同时乘以2,得 2X+2Y=44……③ ②-③,得 X=10 把X=10代入X+Y=22,得 10+Y=22 Y=12 所以,X=10,Y=12,XY=120

谈谭孔1877已知x.y.满足x ²+y ²+5/4=2x+y,求代数式xy/x+y的值. -
余姣印19197679841 ______ (x²-2x+1)+(y²-y+1/4)=0(x-1)²+(y-1/2)²=0 平方相加为0,所以只有两个平方都等于0 所以x-1=0,y-1/2=0 x=1,y=1/2 所以xy/(x+y)=(1/2)/(3/2)=1/3

谈谭孔1877很难的哦:已知X.Y满足X^2+Y^2+5/4=2X+Y,则代数式XY/X+Y的值是多少? -
余姣印19197679841 ______ 解:X^2+Y^2+5/4=2X+Y 移项得:X^2-2X+Y^2-Y+5/4=0 即:X^2-2X+1+Y^2-Y+1/4=0 (X-1)^2+(Y-1/2)^2=0 因为(X-1)^2≥0 (Y-1/2)^2≥0 所以 (X-1)^2=0 (Y-1/2)^2=0哗氦糕教蕹寄革犀宫篓 所以X-1=0 X=1 Y-1/2=0 Y=1/2 所以XY/X+Y=1*1/2÷1+1/2=1

谈谭孔1877已知x,y满足x^2+y^2+5/4=2x+y,求 xy/x+y的值 -
余姣印19197679841 ______ x^2+y^2+5/4=2x+y,==>(x^2-2x+1)+(y^2-y+1/4)=0==>(x-1)^2+(y-1/2)^2=0 则x-1=0 y-1/2=0 x=1,y=1/2 则xy/(x+y)=1*1/2/(1+1/2)=1/3

谈谭孔1877已知x、y满足x2+y2+54=2x+y,则代数式xyx+y的值为______. -
余姣印19197679841 ______[答案] ∵x2+y2+ 5 4=2x+y, ∴x2-2x+1+y2-y+ 1 4=0, ∴(x-1)2+(y- 1 2)2=0, ∴x=1,y= 1 2, 当x=1,y= 1 2时, 原式= 1*12 1+12= 1 3. 故答案是 1 3.

谈谭孔1877已知x2+xy=54,y2+xy=27,求x - y的值. -
余姣印19197679841 ______[答案] ∵x2+xy=54,y2+xy=27, ∴x2+xy-(y2+xy)=54-27, ∴x2-y2=27, ∴(x-y)(x+y)=27, ∵x2+xy+y2+xy=54+27, ∴x2+2xy+y2=54+27, ∴(x+y)2=81, ∴x+y=±9, ∴x-y=81÷(±9)=±9.

谈谭孔1877已知:x,y满足x2+y2+5/4=2x+y,求代数式xy/(x+y)的值 -
余姣印19197679841 ______ x2+y2+5/4=2x+y(x-1)^2+(y-1/2)^2=0 所以 x=1 y=1/2 xy/(x+y)=(1/2)/(3/2)=1/3

谈谭孔1877数学题xy+x+y+1=?为什么? -
余姣印19197679841 ______[答案] xy+x+y+1 =(xy+x)+(y+1) =x(y+1)+(y+1) =(y+1)(x+1)