SOLUTION: I asked this problem earlier, but have learned how to type it so that it is easier for you to read and understand. I need to square this problem. Problem: 2x^2+4x-1=0 Formula I u

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons -> SOLUTION: I asked this problem earlier, but have learned how to type it so that it is easier for you to read and understand. I need to square this problem. Problem: 2x^2+4x-1=0 Formula I u      Log On


   

Question 288296: I asked this problem earlier, but have learned how to type it so that it is easier for you to read and understand. I need to square this problem.
Problem: 2x^2+4x-1=0
Formula I used was: %28-4%2B-sqrt%284%5E2-4%2A2%2A-1%29%29%2F%282%2A2%29
I got:
%28-4%2B-sqrt%2816-4%2A2%2A-1%29%29%2F%282%2A2%29
then %28-4%2B-sqrt%2816%2B8%29%29%2F%282%2A2%29
then %28-4%2B-sqrt%2824%29%29%2F%282%2A2%29
then %28-4%2B-2sqrt%286%29%29%2F%282%2A2%29 (this is supposed to read "+ or - 2" not -2)
then %28-4%2B-2sqrt%286%29%29%2F%284%29 (this is supposed to read "+ or - 2", not -2)
then after simplifying, I get
%28-1%2B-sqrt%286%29%29%2F%282%29
My book says the answer is: %28-2%2B-sqrt%286%29%29%2F%282%29
I can't figure out where I went wrong, so I can't answer my real question of 2x^2+10x-3=0.
Any help is appreciated!! Thank you!
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
Problem: 2x^2+4x-1=0
Formula I used was: %28-4%2B-sqrt%284%5E2-4%2A2%2A-1%29%29%2F%282%2A2%29
I got:
%28-4%2B-sqrt%2816-4%2A2%2A-1%29%29%2F%282%2A2%29
then %28-4%2B-sqrt%2816%2B8%29%29%2F%282%2A2%29
then %28-4%2B-sqrt%2824%29%29%2F%282%2A2%29
then %28-4%2B-2sqrt%286%29%29%2F%282%2A2%29 (this is supposed to read "+ or - 2" not -2)
then %28-4%2B-2sqrt%286%29%29%2F%284%29 (this is supposed to read "+ or - 2", not -2)
then after simplifying, I get
%28-1%2B-sqrt%286%29%29%2F%282%29
My book says the answer is: %28-2%2B-sqrt%286%29%29%2F%282%29
I can't figure out where I went wrong, so I can't answer my real question of 2x^2+10x-3=0.
Any help is appreciated!! Thank you!
------------
You did fine until the last step:
(-4+-2sqrt(6))/(4)
There is a common factor of 2 in the numerator
and in the denominator.
Remove it and cancel it and you get:
(-2+sqrt(6))/2
======================
Cheers,
Stan H.