## Rules for differentiation

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# Rules for differentiation

There are rules or formulas that allow us to evaluate derivatives quickly without explicitly going through the limit process. We shall look at some rules in this section.

Rule. If c is a constant, then

d/dx (c) = 0

That is, the derivative of a constant function is zero.

f ' (x) = lim

h→0

f ' (x) = lim c-c / h = lim 0/h = 0

h→0 h→0

For example, if y = 5, then dv/dx = d 5/dx = 0

That is, the derivative of a constant power of x is the exponent times x raised to a power one less than the given power.

f ' (x) = lim

h→0 h

= lim

h→0 h

= lim

x+h→x (x + h) - x

= n x

Hence f ‘ (c) = n x

For more help in

Rule. If c is a constant, then

d/dx (c) = 0

That is, the derivative of a constant function is zero.

**Proof.**Let f (x) = c. Aapplying the definition of the derivative, we obtainf ' (x) = lim

__f (x+ h) - f (x)__h→0

f ' (x) = lim c-c / h = lim 0/h = 0

h→0 h→0

For example, if y = 5, then dv/dx = d 5/dx = 0

**Rule**. If n is any real number, then d/dx (x^{n}) = n x^{n-1}That is, the derivative of a constant power of x is the exponent times x raised to a power one less than the given power.

**Proof.**We shall give a proof for the case when is a positive integer. Let f (x) = x^{n}. By applying the definition of the derivative, we obtainf ' (x) = lim

__f (x+ h) - f (x)__h→0 h

= lim

__(x + h)__^{n}- x^{n}h→0 h

= lim

__(x+h)__^{n}- x^{n}x+h→x (x + h) - x

= n x

^{n-1 }Hence f ‘ (c) = n x

^{n-1}.For more help in

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