Mister Exam

Sum of series 12a³k³-6a⁴k+2a6k5



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The solution

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  oo                               
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  \   /    3  3      4            \
  /   \12*a *k  - 6*a *k + 2*a6*k5/
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n = 1                              
$$\sum_{n=1}^{\infty} \left(2 a_{6} k_{5} + \left(12 a^{3} k^{3} - 6 a^{4} k\right)\right)$$
Sum((12*a^3)*k^3 - 6*a^4*k + (2*a6)*k5, (n, 1, oo))
The radius of convergence of the power series
Given number:
$$2 a_{6} k_{5} + \left(12 a^{3} k^{3} - 6 a^{4} k\right)$$
It is a series of species
$$a_{n} \left(c x - x_{0}\right)^{d n}$$
- power series.
The radius of convergence of a power series can be calculated by the formula:
$$R^{d} = \frac{x_{0} + \lim_{n \to \infty} \left|{\frac{a_{n}}{a_{n + 1}}}\right|}{c}$$
In this case
$$a_{n} = - 6 a^{4} k + 12 a^{3} k^{3} + 2 a_{6} k_{5}$$
and
$$x_{0} = 0$$
,
$$d = 0$$
,
$$c = 1$$
then
$$1 = \lim_{n \to \infty} 1$$
Let's take the limit
we find
True

False
The answer [src]
   /       4                 3  3\
oo*\- 6*k*a  + 2*a6*k5 + 12*a *k /
$$\infty \left(- 6 a^{4} k + 12 a^{3} k^{3} + 2 a_{6} k_{5}\right)$$
oo*(-6*k*a^4 + 2*a6*k5 + 12*a^3*k^3)

    Examples of finding the sum of a series