Question 373061
if k<>0 : 

y = kx(4-x) => y/k = x(4-x) = 4x - x^2 = -(x-2)^2 + 4
 
-(x-2)^2 = y/k - 4
 
(x-2)^2 = 4 - y/k
 
x-2 = +/-Sqrt(4 - y/k)
 
x = 2 +/- Sqrt(4 - y/k)
 
 
if k=0 : if y=0 any x is solution
 
if k=0 and y<>0 there are no solution.