Lösung 1.2:2e
Aus Online Mathematik Brückenkurs 2
K |
K (Robot: Automated text replacement (-{{Displayed math +{{Abgesetzte Formel)) |
||
Zeile 3: | Zeile 3: | ||
To begin with, we have a product of <math>x</math> and <math>(2x+1)^4</math> so the product rule gives that | To begin with, we have a product of <math>x</math> and <math>(2x+1)^4</math> so the product rule gives that | ||
- | {{ | + | {{Abgesetzte Formel||<math>\begin{align} |
\frac{d}{dx}\,\bigl[x(2x+1)^4\bigr] | \frac{d}{dx}\,\bigl[x(2x+1)^4\bigr] | ||
&= (x)'\cdot (2x+1)^4 + x\cdot \bigl((2x+1)^4\bigr)'\\[5pt] | &= (x)'\cdot (2x+1)^4 + x\cdot \bigl((2x+1)^4\bigr)'\\[5pt] | ||
Zeile 11: | Zeile 11: | ||
We can differentiate the expression <math>(2x+1)^4</math> by viewing it as "something raised to the 4", | We can differentiate the expression <math>(2x+1)^4</math> by viewing it as "something raised to the 4", | ||
- | {{ | + | {{Abgesetzte Formel||<math>\bbox[#FFEEAA;,1.5pt]{\phantom{(2x+1)}\!\!}^{\,4}\,\textrm{.}</math>}} |
The chain rule then gives | The chain rule then gives | ||
- | {{ | + | {{Abgesetzte Formel||<math>\begin{align} |
\frac{d}{dx}\,\bigl[\bbox[#FFEEAA;,1.5pt]{\phantom{(2x+1)}\!\!}^{\,4}\bigr] | \frac{d}{dx}\,\bigl[\bbox[#FFEEAA;,1.5pt]{\phantom{(2x+1)}\!\!}^{\,4}\bigr] | ||
&= 4\cdot \bbox[#FFEEAA;,1.5pt]{\phantom{(2x+1)}\!\!}^{\,3}\cdot \bbox[#FFEEAA;,1.5pt]{\phantom{(2x+1)}\!\!}^{\,\prime}\,,\\[5pt] | &= 4\cdot \bbox[#FFEEAA;,1.5pt]{\phantom{(2x+1)}\!\!}^{\,3}\cdot \bbox[#FFEEAA;,1.5pt]{\phantom{(2x+1)}\!\!}^{\,\prime}\,,\\[5pt] | ||
Zeile 23: | Zeile 23: | ||
We carry out the last differentiation directly, and obtain | We carry out the last differentiation directly, and obtain | ||
- | {{ | + | {{Abgesetzte Formel||<math>(2x+1)' = 2\,\textrm{.}</math>}} |
If we go through the whole calculation from the beginning, it is | If we go through the whole calculation from the beginning, it is | ||
- | {{ | + | {{Abgesetzte Formel||<math>\begin{align} |
\frac{d}{dx}\,\bigl[x(2x+1)^4\bigr] | \frac{d}{dx}\,\bigl[x(2x+1)^4\bigr] | ||
&= (x)'\cdot (2x+1)^4 + x\cdot \bigl((2x+1)^4\bigr)'\\[2pt] | &= (x)'\cdot (2x+1)^4 + x\cdot \bigl((2x+1)^4\bigr)'\\[2pt] | ||
Zeile 37: | Zeile 37: | ||
Both terms contain a common factor <math>(2x+1)^3</math> which we can take out to get an answer in factorized form, | Both terms contain a common factor <math>(2x+1)^3</math> which we can take out to get an answer in factorized form, | ||
- | {{ | + | {{Abgesetzte Formel||<math>\begin{align} |
\frac{d}{dx}\,\bigl[x(2x+1)^4\bigr] | \frac{d}{dx}\,\bigl[x(2x+1)^4\bigr] | ||
&= (2x+1)^3\bigl((2x+1)+8x\bigr)\\[5pt] | &= (2x+1)^3\bigl((2x+1)+8x\bigr)\\[5pt] | ||
&= (2x+1)^3(10x+1)\,\textrm{.} | &= (2x+1)^3(10x+1)\,\textrm{.} | ||
\end{align}</math>}} | \end{align}</math>}} |
Version vom 12:53, 10. Mär. 2009
One way to differentiate the expression could be to expand \displaystyle (2x+1)^4 multiply by \displaystyle x and differentiate term by term, but it is simpler instead to use the structure of the expression and differentiate step by step using the differentiation rules.
To begin with, we have a product of \displaystyle x and \displaystyle (2x+1)^4 so the product rule gives that
\displaystyle \begin{align}
\frac{d}{dx}\,\bigl[x(2x+1)^4\bigr] &= (x)'\cdot (2x+1)^4 + x\cdot \bigl((2x+1)^4\bigr)'\\[5pt] &= 1\cdot (2x+1)^4 + x\cdot \bigl((2x+1)^4\bigr)'\,\textrm{.} \end{align} |
We can differentiate the expression \displaystyle (2x+1)^4 by viewing it as "something raised to the 4",
\displaystyle \bbox[#FFEEAA;,1.5pt]{\phantom{(2x+1)}\!\!}^{\,4}\,\textrm{.} |
The chain rule then gives
\displaystyle \begin{align}
\frac{d}{dx}\,\bigl[\bbox[#FFEEAA;,1.5pt]{\phantom{(2x+1)}\!\!}^{\,4}\bigr] &= 4\cdot \bbox[#FFEEAA;,1.5pt]{\phantom{(2x+1)}\!\!}^{\,3}\cdot \bbox[#FFEEAA;,1.5pt]{\phantom{(2x+1)}\!\!}^{\,\prime}\,,\\[5pt] \frac{d}{dx}\,\bigl[(2x+1)^4\bigr] &= 4\cdot (2x+1)^3\cdot (2x+1)'\,\textrm{.} \end{align} |
We carry out the last differentiation directly, and obtain
\displaystyle (2x+1)' = 2\,\textrm{.} |
If we go through the whole calculation from the beginning, it is
\displaystyle \begin{align}
\frac{d}{dx}\,\bigl[x(2x+1)^4\bigr] &= (x)'\cdot (2x+1)^4 + x\cdot \bigl((2x+1)^4\bigr)'\\[2pt] &= 1\cdot (2x+1)^4 + x\cdot 4(2x+1)^3\cdot (2x+1)'\\[5pt] &= (2x+1)^4 + x\cdot 4(2x+1)^3\cdot 2\\[5pt] &= (2x+1)^4 + 8x(2x+1)^3\,\textrm{.} \end{align} |
Both terms contain a common factor \displaystyle (2x+1)^3 which we can take out to get an answer in factorized form,
\displaystyle \begin{align}
\frac{d}{dx}\,\bigl[x(2x+1)^4\bigr] &= (2x+1)^3\bigl((2x+1)+8x\bigr)\\[5pt] &= (2x+1)^3(10x+1)\,\textrm{.} \end{align} |