Question
Find the derivative of the following functions from first principle: $-\text{x}$

Answer

Let f(x) = –x. Accordingly, f(x + h) = -(x + h) By first principle, $\text{f}'(\text{x})=\lim\limits_{\text{h}\rightarrow0}\frac{\text{f(x+h)}-\text{f(x)}}{\text{h}}$ $=\lim\limits_{\text{h}\rightarrow0}\frac{-(\text{x+h})-(-\text{x})}{\text{h}}$ $=\lim\limits_{\text{h}\rightarrow0}\frac{-\text{x}-\text{h}+\text{x}}{\text{h}}$ $=\lim\limits_{\text{h}\rightarrow0}\frac{-\text{h}}{\text{h}}$ $=\lim\limits_{\text{h}\rightarrow0}(-1)=-1$

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