若圆C：（x-3)^2+（y+5)^2=r^2上有且只有两个点到直线l：4x-3y=2的距离为1,则r的取值范围是多少?

已知x/y+z=y/x+z=z/x+y,分式(x+2y+3z)/(2x+5y-2c)有意义时的值 几道 数学题急啊 对了再加20分(x+y)^2-(x+y)^3(x-y)^2-(x-y)^3 (x-y)^2-(y-x)^32(x-y)-3(y-x)^24ab(a+b)^2-6a^2b(a+b)(x+y)(x-y)-(x+y)^28a(x-y)^2-4b(y-x)a=-5 a+b+c=-5.2求代数式a^2(-b-c)-3.2a(c+b)的值 已知A=3x^2-12,B=5x^2*y^3+10x*y^3,C=(x+1)(x+3)+1求其公因式已知A=3x*x-12,B=5x*x*y*y*y+10x*y*y*y,C=(x+1)(x+3)+1求其公因式,若无,说出理由 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) 求f(x,y)=,max{|（x-y）/（x+2y+3）|,（x+2）/（x+2y+3）,（5y+4）/（x+2y+3）}的最小值用max｛a,b,c｝表示a,b,c三个数中的最大值,设f(x,y)=,max{|（x-y）/（x+2y+3）|,（x+2）/（x+2y+3）,（5y+4）/（x+2y+3）}（x,y∈R 若2x=5y,则下列式子中错误的是() A x/y=5/2 B y/x=2/5 C x+y/x=7/5 D x-y/y=3/2 如果A={（x,y）|x,y+2>0},B={（x,y）|2x+3y-6>0},C={（x,y）|x-4 曲线C：2x^+y^-x+2y-3=0关于y轴对称 已知2y-x=5,则5(x-2y)方-3(x-2y)-60的值是?A.80 B.10 C.210 C.40 （x+y）^2-z^=a^2-(b-c)^2=(x-y)^3-x+y=16(x+y)^2-25(x-y)^2= 设集合A={x|x=y^2-2y-8},B={x|y=-x^2+2x+3},C={y|y+1 下列去括号正确的是：x-(5y-3y)=x-5y-3z C:2x+(-3y+7)=2x-3y-7 B；a-3(b-c+b)=a-3b-3c-3dD:5x-[2y-(x-z)]=5x-2y+x-z x+y/2+x-y/6=5 2(x+y)-3(x-y)=-2 已知多项式A=x^2+2y^2-z^2,B=-4x^2+3y^2+2x^2,且A+B+C=0,则C为A.5x^2-y^2-x^2 B.3x^2-5y^2-z^2 C.3X^2-Y^2-3X^2.D.3X-5Y+Z^2 3(x+y)+2(x-y)=36 4(x+y)-5(x-y)=2 MATLAB三维图像处理：加坐标轴等x=-3:0.02:3;y=-1:0.02:5;[x,y]=meshgrid(x,y);z=0.5*x.^2+0.5*(y+1).^2-log(y+1)-0.5;mesh(x,y,z)x=-3:0.02:3;y=-1:0.02:5;[x,y]=meshgrid(x,y);z=0.5*x.^2+0.5*(y+1).^2-log(y+1)-0.5;C=contour(x,y,z,40);clabel(C)1.怎 (x-y)/(x+y)=3求( 3x-2y-1)/(x+y-5) 4(x-y)-3(x-y)=9 5(x-y)+2(x-y)=11