*f*be specified in surrounding U of a certain point x

_{0}.

*f: f(x) = y.*

Δy is change in value of function that corresponds to change in value of x-variable Δx.

Thus, we have:

*Δy = f(x*

_{0}+ Δx) - f(x_{0}).Difference quotient of a function

*f*in a point x

_{0}with a change Δx of a variable x is, then:

*Δy = (f(x*

_{0}+ Δx) - f(x_{0})) / Δx.Derivative of a function

*f*in point

*x*, noted as

_{0}*f'(x*is difference quotient limit at

_{0})*Δx → 0*.

Thus, we have:

Source: [42].

See also, if You wish: Differential of a function.

(EN) derivative of a function f in a point = (PL) różniczka funkcji f w punkcie.

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