Given y=x^2+2x
y+dy=(x+dx)^2+2(x+dx)
dy=x^2+2xdx+(dx)^2+2x+2dx-y
but
y=x^2+2x
dy=x^2+2xdx+(dx)^2+2x+2dx-(x^2+2x)
dy=2xdx+(dx)^2+2dx
dy/dx=(dx(2x+dx+2))/xd
dy/dx=2x+dx+2
the limit of dy/dx as dx approaches 0 will be....
Limit dy/dx=2x+2
There fore the limit of f(x)= 2x+2