Need help with basic dervivative problem

[TheKracken]

Homework Statement

they want f'(x)
of f(x)=2x^2 +x-1

Homework Equations

I know how to use the power rule and such and get that answer to be 4x+1...but I am practicing using the definition of a dervivative and I keep getting 4x-1
...so you need help

relevent equations: f'(x)= Lim h→0 of f(x+h) - f(x) all over h

The Attempt at a Solution

started out with
2(x+h)^2 +(x+h) -(2x^2 +x-1) all over h

then I got 2x^2 +2h^2 +2xh +x+h-1-2x^2 - x +1 all over h

and cancled out and got
2h^2 +4xh +h -1 all over h

then I factored out the h and got
h(2h+4x)-1 all over h

cancled out the h and got
2h+4x-1 all over 1

entered in 0 for h and i got 4x-1
so what the heck did I do wrong? haha, I think I had my set up wrong from the beginning? anyone willing to help me out here, just started self studying calculus so a little confused...

 

[eumyang]

started out with
2(x+h)^2 +(x+h) -(2x^2 +x-1) all over h

This is wrong. It should be
$$\frac{2(x + h)^2 + (x + h) \textbf{ - 1} - (2x^2 + x - 1)}{h}$$

then I got 2x^2 +2h^2 +2xh +x+h-1-2x^2 - x +1 all over h

This isn't right either. This should be
$$\frac{2x^2 + \textbf{4xh} + 2h^2 + x + h - 1 - 2x^2 - x + 1}{h}$$

and cancled out and got
2h^2 +4xh +h -1 all over h

Nope. This should be
$$\frac{4xh + 2h^2 + h}{h}$$
You should be able to figure out the rest from here.

 

[TheKracken]

right i got it...wrong set up, thank you very much :) now I see how to set those up haha, thank you.