已知2x=3,2y=6-搜答案-神马作文网

3(y-7)-6(x-y)=3y-21-6x+6y=9y-6x-21=3(3y-2x)-21=3*(-7)-21=-42

x+3y=0x^3+3x^2y-2x-6y=x^2(x+3y)-2(x+3y)=0-0=0

很多数学符号,还是写出来方便.

x^3+3x^2y-2x-6y=x²(x+3y)-2(x+3y)=0-0=0

=x^2(x+3y)-2*(x+3y)=0

(1)已知x+y=6,x²-y²=5,x^2-y^2=(x+y)(x-y)=5x-y=5/(x+y)=5/6（2）若x+y=3,x²+y²=5(x+y)^2=3

[(2x+6)/(x^2-2xy+y^2)]*(x-y)是不是给错了,应该是[(2x+6y)/(x^2-2xy+y^2)]*(x-y)吧?x-3y=0得x=3y代入[(2x+6y)/(x^2-2xy+

X+Y分之X-Y等于3x=-2yX+Y分之2(x-y)减X+Y分之3X+Y=(-x-3y)/(x+y)=1

在坐标系中先作2x+5y≥10对应的直线2x+5y=10,取直线上方区域；然后作2x-3y≥-6对应的直线2x-3y=-6,把y的系数变为正,可知取直线下方区域；最后作2x+y≤10对应的直线2x+y

因为(x-y)/(x+y)=3,则(x＋y)/(x－y)＝1/3则5(x-y)(x+y)-(x+y)/2(x-y)＝5*3-1/(3*2)=15-1/6=89/6

（x+y)（x-y)-y^2+（x-y)^2-（6x^2y-2xy^2)÷2y=（x+y)（x-y)-y^2+（x-y)^2-2y（3x^2-xy)÷2y=（x+y)（x-y)-y^2+（x-y)^2

(x+y)(x-y)-y^2+(x-y)^2-(6x^2y-2xy^2)/(2y)=X^2-y^2-y^2+X^2+y^2-2xy-3x^2+xy=-x^2-y^2-xy=-(x^2+y^2+xy-3

x-y=3（x-y)^2=9x^2-2xy+y^2=9x^2+y^2=13（x+y）（x-y）-y^2-（6x^2y-2xy^2)/2y=x^2-y^2-y^2-3x^2+xy=-2(x^2+y^2)

x-5y=0x=5y所以(2x-3y)/(3x+6y)=(10y-3y)/(15y+6y)=7y/21y=1/3

x-2y=3则：x=2y+3代入原式,原式=(4y+6+y-6)/(6y+9-y-9)=5y/5y=1

(x³+y³)+(x²y+xy²)+(x+y)=0(x+y)(x²-xy+y²)+xy(x+y)+(x+y)=0(x+y)(x²-

(x+y)(x-y)-y²+(x-y)²-(6x²y-2xy²)÷(2y)=x²-y²-y²+x²-2xy+y²

不会

（6x+2y)/(9x-3y)=6(6x/y+2)/(9x/y-3)=6,解得：x/y=5/12(3x+y)^2/(x^2-y^2)=(3x/y+1)^2/((x/y)^2-1)=(81/16)*(2

是不是(3x+4)²+y²-6y+9=0(3x+4)²+(y-3)²=0∴3x+4=0y-3=0∴x=-4/3y=3∴x+y=-4/3+3=5/4