Online Course Discussion Forum

Math Challenge II-A 2.28

 
 
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Math Challenge II-A 2.28
by Zhi Feng Etan Kiang - Sunday, 14 June 2020, 6:21 PM
 
Hello! May you please help me with problem 2.28 on this week's (June 10-17) assignment? I tried making the Vieta's Formulas and substituting them into each other, but it did not work. Please help me. Thank you!
 
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Re: Math Challenge II-A 2.28
by Areteem Professor - Tuesday, 16 June 2020, 11:25 PM
 

When you have a quadratic equation of the form $ax^2 + bx + c =0$, Vieta's formulas tell you that the roots, $x_1$ and $x_2$, are such that $x_1 + x_2 = \dfrac{-b}{a}$, and $x_1x_2 = \dfrac{c}{a}$.

Use these to rewrite $x_1^2 + x_2^2$ in terms of $a$, $b$, and $c$ only.