Question 1 Report
Differentiate, with respect to x, \(x^{3} + 2x\) from the first principle.
Differentiate \(f(x)=x^3+2x\) from first principles.
By definition,
\[f'(x)=\lim_{h\to0}\frac{f(x+h)-f(x)}{h}.\]
Compute \(f(x+h):\)
\[f(x+h)=(x+h)^3+2(x+h)=x^3+3x^2h+3xh^2+h^3+2x+2h.\]
Then
\[f(x+h)-f(x)=3x^2h+3xh^2+h^3+2h.\]
Divide by \(h\) (for \(h\neq0\)):
\[\frac{f(x+h)-f(x)}{h}=3x^2+3xh+h^2+2.\]
Now let \(h\to0:\)
\[f'(x)=\lim_{h\to0}\left(3x^2+3xh+h^2+2\right)=3x^2+2.\]
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