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Find from first principles the derivative of f(x)= root of X with respect to x

Sagot :

To find:

The derivative of function f(x) using the first principle.

[tex]f(x)=\sqrt{x}[/tex]

Solution:

By the first principle, the derivative of the function f(x) is given by:

[tex]f^{\prime}(x)=\lim_{h\to0}\frac{f(x+h)-f(x)}{h}[/tex]

So, the derivative of the given function can be obtained as follows:

[tex]\begin{gathered} f^{\prime}(x)=\lim_{h\to0}\frac{\sqrt{x+h}-\sqrt{x}}{h} \\ =\lim_{h\to0}\frac{\sqrt{x+h}-\sqrt{x}}{h}\times\frac{\sqrt{x+h}+\sqrt{x}}{\sqrt{x+h}+\sqrt{x}} \\ =\lim_{h\to0}\frac{x+h-x}{h(\sqrt{x+h}+\sqrt{x})} \\ =\lim_{h\to0}\frac{h}{h(\sqrt{x+h}+\sqrt{x})} \\ =\lim_{h\to0}\frac{1}{(\sqrt{x+h}+\sqrt{x})} \\ =\frac{1}{\sqrt{x+0}+\sqrt{x}} \\ =\frac{1}{2\sqrt{x}} \end{gathered}[/tex]

Thus, the derivative of the given function is:

[tex]f^{\prime}(x)=\frac{1}{2\sqrt{x}}[/tex]