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math 2a

 
 
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math 2a
by shawn luo - Saturday, 8 August 2020, 2:02 PM
 

I don't understand problems. 9.17 and 9.18

 
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Re: math 2a
by Areteem Professor - Monday, 10 August 2020, 11:53 AM
 

For 9.17 you can use Vieta's formulas to find the sum of the roots. For a polynomial $P(x) = a_{n}x^{n}+a_{n-1}x^{n-1}+\cdots+a_{1}x+a_0$, the sum of all roots (real and complex, with multiplicities) is equal to $-\dfrac{a_{n-1}}{a_{n}}$.

For 9.18, let $x_1, \dots, x_5$ be the five roots. Since they are all solutions to the equation, we have their fifth powers can be written as $x_{i}^5 = -2x_{i} +1$ for $i = 1, \dots, 5$. You can use this to write a simpler expression for the sum of the fifth powers. You might need to use Vieta's formulas to finish.