x+y=450(1-0.6)x=(1-0.4)y-30这个方程组肿麽解啊 告我吧 着急

mathematica软件,已知y[x],Y=f1(x),X(x)=f2(x),如何plot Y[X]?y[x_] := x + 9.81/2*x*xk=1X[x] = x - k*y'[x]/(1 + (y'[x])^2)^0.5Y[x] = y[x] + k/(1 + (y'[x])^2)^0.5Plot[{y[x],Y[X],},{x,0,2}] 设x大于1,y大于0,x^y+x^-y=2根号二,x^y-x^-y等于? x>=1,x-y y=x-1(x y=1-x^2 x>=0 ,y=sin|x|/x x 若实数x,y满足x-y+1》=0,x+y>=0,x 已知x,y满足约束条件：x-y+1>=0,x+y-2>=0,x 若实数x,y满足x-y+1>=0,x+y>=0,x 画出不等式组x+y>0,x=还有不等式（x-y)(x-y-1)= y=1/x^2(x>0) y=(1-x)/(1+x) y=(e^x-e^-x)/2 若x+y=1,x不等于0则x+(2xy+y^2)/x/(x+y)/x= 求导 y=[x/(1+x)]^x y=x(1-x) (0 若2x-3y+4=0则x（x*x-1)+x(5-x*x)-6y+7 y'-(1/x)y=xe^-x 已知x^2+y^2-8x+12y+52=0 ,求1/2x-1/x-y(x-y/2x-x^2+y^2) 已知x^2+y^2-8x+12y+52=0 ,求1/2x-1/x-y(x-y/2x-x^2+y^2) 已知x²+y²+6x-8x+25=0,求（x/x²-y² - 1/x+y）÷y/y-x