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Let  and  be the roots of the quadratic equation 2x^2 - 8x + 7. Find 1/(2a) +1/(2b)
 

 Jun 10, 2016
 #1
avatar+2498 
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\(\text{use the quadratic formula :} \\x = {-b \pm \sqrt{b^2-4ac} \over 2a}\)

 

here is the roots:

http://www.cymath.com/answer.php?q=2x%5E2-8x%2B7%3D0

 Jun 10, 2016
 #2
avatar+9466 
0

Don't use the quad. formula because i have a faster way.

 

In the quad. eq. ax2+bx+c=0

Sum of the 2 sol. = \(-\frac{b}{a}\)

Product of the 2 sol. = \(\frac{c}{a}\)

 

a and b are the 2 roots of the equation in your question.

Let's make it \(\alpha\)and\(\beta \)

\(\frac{1}{2\alpha}+\frac{1}{2\beta}\)

\(\frac{\alpha+\beta}{2\alpha\beta}\)

=\(\frac{-\frac{-8}{2}}{\frac{(2)(7)}{2}}\)

\(\frac{4}{7}\)

 Jun 11, 2016

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