Approximation of a differentiable function.












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If $Doverset{f}{rightarrow}mathbb{C}$ is differentiable in $x_0$ $(Dsubseteqmathbb{R})$, the closer one gets to $x_0$ the smaller the difference between the linear function $l_{x_{0}}(x)=f(x_0)+f'(x_0)(x-x_0)$ gets. The Approximation is defined as:



$$begin{align}
r_{x_{0}}(x) &:=f(x)-l_{x_{0}}(x)\
&=f(x)-f(x_0)-f'(x_0)(x-x_0) \
&=left(frac{f(x)-f(x_0)}{x-x_0}-f'(x_0)right)(x-x_0)
end{align}$$



How does one conclude that the left factor on the very Right side converges to $0$.



And how does one conclude by that that



$lim_{xrightarrow x_0}frac{r_{x_{0}}(x)}{x-x_0}=0$










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$endgroup$












  • $begingroup$
    the limit of the left factor is zero by definition of derivative at $x_0$
    $endgroup$
    – GReyes
    Jan 19 at 20:13












  • $begingroup$
    You divide by $(x-x_0)$ both sides and use the fact that that left factor converges to zero
    $endgroup$
    – GReyes
    Jan 19 at 20:18
















0












$begingroup$


If $Doverset{f}{rightarrow}mathbb{C}$ is differentiable in $x_0$ $(Dsubseteqmathbb{R})$, the closer one gets to $x_0$ the smaller the difference between the linear function $l_{x_{0}}(x)=f(x_0)+f'(x_0)(x-x_0)$ gets. The Approximation is defined as:



$$begin{align}
r_{x_{0}}(x) &:=f(x)-l_{x_{0}}(x)\
&=f(x)-f(x_0)-f'(x_0)(x-x_0) \
&=left(frac{f(x)-f(x_0)}{x-x_0}-f'(x_0)right)(x-x_0)
end{align}$$



How does one conclude that the left factor on the very Right side converges to $0$.



And how does one conclude by that that



$lim_{xrightarrow x_0}frac{r_{x_{0}}(x)}{x-x_0}=0$










share|cite|improve this question











$endgroup$












  • $begingroup$
    the limit of the left factor is zero by definition of derivative at $x_0$
    $endgroup$
    – GReyes
    Jan 19 at 20:13












  • $begingroup$
    You divide by $(x-x_0)$ both sides and use the fact that that left factor converges to zero
    $endgroup$
    – GReyes
    Jan 19 at 20:18














0












0








0





$begingroup$


If $Doverset{f}{rightarrow}mathbb{C}$ is differentiable in $x_0$ $(Dsubseteqmathbb{R})$, the closer one gets to $x_0$ the smaller the difference between the linear function $l_{x_{0}}(x)=f(x_0)+f'(x_0)(x-x_0)$ gets. The Approximation is defined as:



$$begin{align}
r_{x_{0}}(x) &:=f(x)-l_{x_{0}}(x)\
&=f(x)-f(x_0)-f'(x_0)(x-x_0) \
&=left(frac{f(x)-f(x_0)}{x-x_0}-f'(x_0)right)(x-x_0)
end{align}$$



How does one conclude that the left factor on the very Right side converges to $0$.



And how does one conclude by that that



$lim_{xrightarrow x_0}frac{r_{x_{0}}(x)}{x-x_0}=0$










share|cite|improve this question











$endgroup$




If $Doverset{f}{rightarrow}mathbb{C}$ is differentiable in $x_0$ $(Dsubseteqmathbb{R})$, the closer one gets to $x_0$ the smaller the difference between the linear function $l_{x_{0}}(x)=f(x_0)+f'(x_0)(x-x_0)$ gets. The Approximation is defined as:



$$begin{align}
r_{x_{0}}(x) &:=f(x)-l_{x_{0}}(x)\
&=f(x)-f(x_0)-f'(x_0)(x-x_0) \
&=left(frac{f(x)-f(x_0)}{x-x_0}-f'(x_0)right)(x-x_0)
end{align}$$



How does one conclude that the left factor on the very Right side converges to $0$.



And how does one conclude by that that



$lim_{xrightarrow x_0}frac{r_{x_{0}}(x)}{x-x_0}=0$







real-analysis






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Jan 19 at 21:13









BigbearZzz

8,88821652




8,88821652










asked Jan 19 at 19:54









RM777RM777

36912




36912












  • $begingroup$
    the limit of the left factor is zero by definition of derivative at $x_0$
    $endgroup$
    – GReyes
    Jan 19 at 20:13












  • $begingroup$
    You divide by $(x-x_0)$ both sides and use the fact that that left factor converges to zero
    $endgroup$
    – GReyes
    Jan 19 at 20:18


















  • $begingroup$
    the limit of the left factor is zero by definition of derivative at $x_0$
    $endgroup$
    – GReyes
    Jan 19 at 20:13












  • $begingroup$
    You divide by $(x-x_0)$ both sides and use the fact that that left factor converges to zero
    $endgroup$
    – GReyes
    Jan 19 at 20:18
















$begingroup$
the limit of the left factor is zero by definition of derivative at $x_0$
$endgroup$
– GReyes
Jan 19 at 20:13






$begingroup$
the limit of the left factor is zero by definition of derivative at $x_0$
$endgroup$
– GReyes
Jan 19 at 20:13














$begingroup$
You divide by $(x-x_0)$ both sides and use the fact that that left factor converges to zero
$endgroup$
– GReyes
Jan 19 at 20:18




$begingroup$
You divide by $(x-x_0)$ both sides and use the fact that that left factor converges to zero
$endgroup$
– GReyes
Jan 19 at 20:18










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