lf f:R→R such that f(x+y)−Kxy=f(x)+2y2 for all x,y∈R and f(1)=2,f(2)=8 then f(20)−f(10)
Let f:R→R be a function satisfying f(x+y)=f(x)+2y2+kxy for all x,yϵR. If f(1) = 2 and f(2) = 8, then f(x) is equal to.