If you know about the power rule,
d/dw (2w² + 1) = 2 d/dw (w²) = 2 • 2w = 4w
If you have to use the limit definition of the derivative, let f(w) = 2w² + 1. Then
[tex]f'(w)=\displaystyle\lim_{h\to0}\frac{f(w+h)-f(w)}h[/tex]
[tex]f'(w)=\displaystyle\lim_{h\to0}\frac{(2(w+h)^2+1)-(2w^2+1)}h[/tex]
[tex]f'(w)=\displaystyle\lim_{h\to0}\frac{2(w^2+2wh+h^2)-2w^2}h[/tex]
[tex]f'(w)=\displaystyle\lim_{h\to0}\frac{4wh+2h^2}h[/tex]
[tex]f'(w)=\displaystyle\lim_{h\to0}(4w+2h)=\boxed{4w}[/tex]
