x^a.y^b=(x+y)^(a+b)
=> ln(x^a.y^b) = ln((x+y)^(a+b))
=>a lnx + b lny = (a+b)ln(x+y)
=>a. d/dx lnx + b. d/dx lny = (a+b). d/dx ln(x+y)
=> a/x + b/y. dy/dx = (a+b)/(x+y). dy/dx
The last line is where I think I made a mistake. Can you please help?
the variables x and y are positive and related by x^a.y^b=(x+y)^(a+b) where a and b are positive constants. By taking logarithms of both sides, show that dy/dx=y/x. provided that bx not equal to ay.