已知已知3x=2,2y=1,则8的x次方·4的2y次方=?-搜答案-智慧作业帮

2x-3y=0(1)3x-y-1=0(2)由（2）得y=3x-1(3)把y=3x-1代入(1)得2x-9x+3=0∴x=3/7把x=3/7代入（3）得y=2/7∴x=3/7y=2/7

3x-3=2y-33x=2yx=2y/3x-y/x+y=(y/3)/(5/3)=1/5

把x-y=-3y+5的左边移到右边：x-y+3y-5=0所以：x+2y-5=0x+2y-1=4

如果楼主说的是1/2为底数的话令f(x)=(3-x)(1-x)则f(x)=x^2-4x+3=(x-2)^2-1所以f(x)的值域是[0,正无穷)因此log1/2[(3-x)(1-x)]的值域是(负无穷

2x-y/x+2y是(2x-y)/(x+2y)吧(2x-y)/(x+2y)=(2x/y-1)/(x/y+2)=(2X2/3-1)/(2/3+2)=1/3÷8/3=1/8

由已知1x+1y=（1x+1y）（x+2y）×14=（3+2yx+xy）×14≥（3+2 2yx×xy）×14=3+224．等号当且仅当2yx＝xy时等号成立．∴1x+1y的最小值为3+22

3x=8yx/y=8/3（1）x+y/y=x/y+1=8/3+1=11/3(2)2x+3y/x-2y分子分母同时除以y得=(2x/y+3)/(x/y-2)=(16/3+3)/(8/3-2)=(25/3

3x-4y/2x+y=1/26x-8y=2x+y4x=9yx/y=9/4

1.y=（-x+10）/3（x不等-2,y不等4）2.原式=1/x+1

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

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-2y/2x+3y=3/44(x-2y)=3(2x+3y)4x-8y=6x+9y-2x=17yx/y=-17/2

4x=9yx=9/4*y(1)(x+y)/y=[(9/4)y+y]/y=(9/4+1)y/y=9/4+1=13/4(2)(y-x)/2x=[y-(9/4)y]/[2*(9/4)y]=(1-9/4)y/

3X+4Y=23X=2-4YX=(2-4Y)/3X-Y-1/7D

原式=(x-y)²-3(x-y)+1=3²-3×3+1x-y用3代替=1再问：3X+3Y是怎么转化成这个的3(X-Y)，什么理由再答：是-3x+3y不是3x+3y

1）x-5y/x+y=2y-5y/2y+y=-12)x=3z/5,y=4z/52x²-3xy+2xz/2y²-4x²+z²=（18z²/25-36z&

(x-2y)/(3y-x)=2/33(x-2y)=2(3y-x)3x-6y=6y-2x5x=12y,代入原方程检验通过,故y/x=5/12

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

1/x+2/y=1,则x+y=(x+y)*1=(x+y)(1/x+2/y)=1+2+2x/y+y/x≥3+2√[(y/x)*(2x/y)]=3+2√2则最小值为3+2√2

5x+xy-5y/x+2y-y?应该是：(5x+xy-5y)/(x+2xy-y)吧!解析：已知x分之1-y分之1=3,那么：(xy)分之(y-x)=3即y-x=3xy所以：(5x+xy-5y)/(x+