))B.-1C.0)))A.-4B.4C.-2D.2)))B.2,-1D.-2,-1))B.mC.m,那么x+y的值為____________.14.若(2x-3y+5)2+|x+y-2|=0,則5x+10y=____________.15.如果x-y=-8,y-z=6,那么z-x的值是____________.文2x+3y,3x+4y,3z.例如:明文1,2,3對應(yīng)密文8,11,9.當(dāng)接收方收到值為____________.的解為____________.甲:x表示__________________,y表示__________________;乙:x表示__________________,y表示_______________;由題意得:n+2=1,|m|+n=1,m+2n4x+3y=7,得7y=7,解得y=1,所以x=y=1,把x=y=1代入ax+(a-1)y=5,得a+a-1=5,解得a=3.故選C.,由題意,得mx+3=(2m-1)x+4,即關(guān)于x的方程(m-1)x=-1有唯一解,故m16.【答案】3,2,9解：由x+y=p,得x=p-y,代入2x+3y=5得:y=5-2p,又x,y為正數(shù),p為將x=2代入②,得2-y=1,解得y=1.把a=代入④得+3b=8,解得b=,把a=,b=代入①得+-c=3,解得20.解:(1)①22.解:(1)20;180;180;20;②-③,得4x=20,解得x=5.②×12,得x+1.5y=240,③20×16=320(錢);若一次性定客房18間,則需付費20×18×0.8=288(錢),288錢<320a1x+b1y=c1a2x+b2y=c23x-5y=92x+2y=52x+2y=83t+2s=5ts+6=02x+3y=0例：在方程2x+3y=18中，用含x的代數(shù)式表示y為：___________,用含y的代數(shù)式表例：已知方程(a-2)x^(/a/-1)-(b+5)y^(b^2-24)=3是關(guān)于x、y的二元一次方程，求,6-(4/3)y>0所以，0<x<6,0<y<9/2舍去；當(dāng)y=3時，x=6-12/3=2所以，3x+4y=18的正整數(shù)解為：x=2當(dāng)y=2時，x=6-8/3=10/3，當(dāng)y=4時，x=6-16/3=2/3，ax-2y=52x+by=3ax+5y=15,①4x-by=-2,②x=-3,y=-1,x=5,y=4,4y-(2y+x+16)/2=-6x2y+3x=7-2x-yx/2+y/3=13/2x/3-y/4=3/2例：ⅰ、解方程組：5/(x+1)+4/(y-2)=27/(x+1)-3/(y-2)=13/20a=8.3ⅱ、已知方程組3a+5b=30.9的解是b=1.2，則方程組2(x+2)-3(y-1)=133(x+2)+5(y-1)=30.9x=8.3A.y=1.2x=10.3B.y=2.2x=6.3C.y=2.2x=10.3D.y=0.2解方程組：2x-y=6(x+2y)(4x-2y)=192②即x+2y=16④③，把①代入③得：(x+2y)×2×6=192,2x-y=6x+2y=16x=5.6y=5.2（1）若︱m+n-5︱+(2m+3n-5)2=0,求(m-n)2的值。5x+y=3x-2y=55x+ny=13x-5y=2m2x-y=k3x+y=k+1=倍數(shù)×倍量；少kg？3x+4y+z=14x+5y+2z=172x+2y-z=33x+4z=7