Q 62 - Calculus

Question

In exercises 59-62 concern the binomial series to find the maclaurin series for the given function .

$(1+x{)}^{2/3}$

Step-by-Step Solution

Answer

The maclaurin series for the given function is

$(1+x{)}^{\frac{2}{3}}=1+\frac{2}{3}x-\frac{1}{9}{x}^2+\frac{4}{81}{x}^3+\cdots$

Step 1. Given information

We have been given 

$(1+x{)}^{2/3}$

to find the maclaurin series by using binomial series 

Step 2.Defining the series

For any non- zero constant  p, the Maclaurin series for the function  $g\left(x\right)=(1+x{)}^p$

 is called the binomial series which is given by   $\sum _{k=0}^{\mathrm{\infty }} \left(\begin{array}{l}p\\ k\end{array}\right)x^k$

 where the binomial coefficient is

$\left(\begin{array}{l}p\\ k\end{array}\right)=\left\{\begin{array}{r}\frac{p(p-1)(p-2)\cdots (p-k+1)}{k!},\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\text{ if }k>0\\ 1,\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\text{ if }k=0\end{array}\right.$

Step 3. Binomial series for the given function is

So for the given function  $f\left(x\right)=(1+x{)}^{\frac{2}{3}}$ binomial series is ,

$(1+x{)}^{\frac{2}{3}}=\sum _{k=0}^{\mathrm{\infty }} \left(\begin{array}{l}\frac{2}{3}\\ k\end{array}\right)x^k$

implies that ,

$\begin{array}{r}(1+x{)}^{\frac{2}{3}}=\left(\begin{array}{c}\frac{2}{3}\\ 0\end{array}\right)x^0+\left(\begin{array}{c}\frac{2}{3}\\ 1\end{array}\right)x^1+\left(\begin{array}{c}\frac{2}{3}\\ 2\end{array}\right)x^2+\left(\begin{array}{c}\frac{2}{3}\\ 3\end{array}\right)x^3+\cdots \\ =1+\frac{2}{3}x+\frac{\frac{2}{3}\left(-\frac{1}{3}\right)}{2!}{x}^2+\frac{\frac{2}{3}\left(-\frac{1}{3}\right)\left(-\frac{4}{3}\right)}{3!}{x}^3+\cdots \\ =1+\frac{2}{3}x-\frac{1}{9}{x}^2+\frac{4}{81}{x}^3+\cdots \end{array}$

Step 4. The maclaurin series for given function is

The maclaurin series for the given function is $(1+x{)}^{\frac{2}{3}}=1+\frac{2}{3}x-\frac{1}{9}{x}^2+\frac{4}{81}{x}^3+\cdots$