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December 19, 2014

December 19, 2014

Posted by **Sheila** on Wednesday, September 7, 2011 at 7:53pm.

What are the roots of the equation and answers have to be simplified

2x^2 + 5x-10 =0

2x^2 + 5x-10+10=0+10

2x^2 + 5x = 10

2x^2 + 5x/2 = 10/2

2x^2/2 + 5x/2 = 5

x^2 + 5/2x = 5

(5/2 * 1/2)^2 = 5/4^2

x^2 + 5/2x + (5/4)^2 = 5 + (5/4)^2

(x+5/4)^2 = 105/16

x + 5/4 = +minus sqrt 105/16 = sqrt 3^1 * 5^1*7^1 = sqrt 105/4

x= -5/4 + sqrt105/4 or x= -5/4 - sqrt 105/4 Is this correct and simplified as far as it can be?

thank you Someone suggested a site that will do it but I want to learn on my own

- Pre-Calc -
**bobpursley**, Wednesday, September 7, 2011 at 8:03pmat this point...

x^2 + 5/2x =5

you want to complete the square, take 1/2 of 5/2, square it, and add it to both sides.

x^2+5/2 x + 25/16=5+25/16=105/16

(x+5/4)^2=(sqrt 105/16)^2

so we agree. I didn't follow your work.

http://www.youtube.com/watch?v=xGOQYTo9AKY

- Pre-Calc-bob pursley recheck please -
**Sheila**, Wednesday, September 7, 2011 at 8:27pmI thought that once I got to 105/16 I should take the square root which is factored out so I can't take anything out of the 105,however I can take the square root of 16 = 4 and you take the square root of (x+5/4)^2 to get it out of parentheses, so therefore the 2 roots are x= -5/4 + or minus square root of 105/4 as the simplified version

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