(1 3x-y)(-1 3x-y)-搜答案-拍题作业网

1.x=1y=1.72.2983.248189

x*x+y*y-4x+6y+13=0(x^2-4x+4)+(y^2+6y+9)=0(x-2)^2+(y+3)^2=0x-2=0,y+3=0x=2,y=-3

x^2+y^2+4x-6y+13=(x+2)^2+(y-3)^2=0所以x=-2y=3所以x^y=-8

由已知可得（X-3)(X-3)+(Y+2)(y+2）=0,即可得X=3.Y=-2,待到问题中即可得到答案为1

x²+y²+4x-6y+13=0x²+4x+4+y²-6y+9=0(x+2)²+(y-3)²=0∴x+2=0y-3=0∴x=-2y=3再问：

x=1/3y=1/2x-(x+y）+（x+2y)-(x+3y)+...-(x+13y)=6y-13y=-7y=-7/2=-3.5

x平方+y平方-4x+6y+13=0(x-2)^2+(y+3)^2=0x=2,y=-3;带入要求的表达式即可.再问：怎么算出x=2y=-3的？？？再答：例如：a^2+b^2=0就只有a=0,b=0才成

2y错了即(x²-4x+4)+(y²+6y+9)=0(x-2)²+(y+3)²=0所以x-2=0,y+3=0x=2,y=-3

x²+y²+13-4x+6y=0(x²-4x+4)+(y²+6y+9)=0(x-2)²+(y+3)²=0平方项恒非负,两非负项之和=0,两非

x*x+y*y-4x-6y+13=0可以化为：(x-2)^2+(y-3)^2=0只有在x=2、y=3时,上式才能成立.代入3x+4y=3*2+4*3=18

x-y=13 x=6y-7

将x=6y-7代入得6y-7-y=135y=20y=4x=24-7=17

(1){x=y-3{x+y=11y-3+y=112y=14y=7x=y-3=7-3=4所以原方程组的解为x=4,y=7(2){2x+y=13{3x-2y=8y=13-2x3x-2(13-2x)=83x

第一题：（x-y)/13=y/713y=7x-7y20y=7xx/y=20/7两边都加1（x+y)/y=27/7第二题：x/6=y/4=z/3（x,y,z,不为零）用特值法令x/6=y/4=z/3=1

{(x,y) |x|+|y|

区域是一个正方形

一、(x-y)^5÷(y-x)^2-(x-y)=(x-y)^5÷(x-y)^2-(x-y)=(x-y)^3-(x-y)=(x-y)[(x-y)^2-1]=(x-y)(x-y+1)(x-y-1)二、(2

x²+4y²-6x+8y+16=0(x²-6x+9)+4(y²+2y+1)=0(x-3)²+4(y+1)²=0x-3=0,y+1=0x=3,

X+y=55X-y=13X=3y=5再答：点错了y=2

27/7绝对正确!

x>y?x:y

判断X的数值是否大于Y的数值如果是则为真等式去X的值反之取Y的值

x²+y²-4x+6y+13=0x²-4x+4+y²+6y+9=0(x-2)²+(y+3)²=0x=2,y=-3代入即可得出答案(3x+y)