SOLUTION: c.. how do i complete the square for this one. i started it but i am confused. Solve by completing the square: 2x^2+8x+3=0 this is how i started but i think i am wrong.

Algebra ->  Algebra  -> Quadratic Equations and Parabolas -> SOLUTION: c.. how do i complete the square for this one. i started it but i am confused. Solve by completing the square: 2x^2+8x+3=0 this is how i started but i think i am wrong.      Log On

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Question 79089: c..
how do i complete the square for this one. i started it but i am confused.
Solve by completing the square: 2x^2+8x+3=0

this is how i started but i think i am wrong...

2x^2+8x+3=0
x^2+8x=(-3)/(2)
x^2+8x+(0.5 (8))^2=(-3)/(2)(0.5(8))^2
i don't know can someone help me i think i am doing it wrong...
Answer by josmiceli(6784) About Me  (Show Source):
You can put this solution on YOUR website!
2x%5E2+%2B+8x+%2B+3+=+0
subtract 3 from both sides
2x%5E2+%2B+8x+=+-3
divide both sides by 2
x%5E2+%2B+4x+=+-%283%2F2%29
Now you operate on the left side to complete square
and put the same thing on both sides so the equation is not changed
x%5E2+%2B+4x+%2B+%284%2F2%29%5E2+=+-%283%2F2%29+%2B+%284%2F2%29%5E2
x%5E2+%2B+4x+%2B+4+=+5%2F2
%28x+%2B+2%29%5E2+=+5%2F2
%28x+%2B+2%29+=+0+%2B-+sqrt%285%2F2%29
x+=+-2+%2B-+sqrt%285%2F2%29 answer
You can check these answers by plugging back into original
equation. It's a good excercise for you