SOLUTION: I need help I have solve this quadratic equation, and I want to know if its right is there a way to check? {{{2x^2-4x-3=0}}}...my answer is x=1+ - 2sqrt(5). thank you.

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons -> SOLUTION: I need help I have solve this quadratic equation, and I want to know if its right is there a way to check? {{{2x^2-4x-3=0}}}...my answer is x=1+ - 2sqrt(5). thank you.      Log On


   



Question 426848: I need help I have solve this quadratic equation, and I want to know if its right is there a way to check?
2x%5E2-4x-3=0...my answer is x=1+ - 2sqrt(5).
thank you.

Found 2 solutions by stanbon, robertb:
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
2x^2-4x-3=0
---
x = [4 +- sqrt(16-4*2*-3)]/4
---
x = [4 +- sqrt(40)]/4
---
x = [1 +- (1/2)sqrt(10)]
=============================
Cheers,
Stan H.
===========

Answer by robertb(5830) About Me  (Show Source):
You can put this solution on YOUR website!
Divide both sides of the equation by 2, to get x%5E2-2x-3%2F2+=+0. For complex or radical roots, the conjugate must also be a root. The conjugate of the root that you got is 1+%2B+2sqrt%285%29.
The sum of the roots must be equal to -(-2), or 2. This is true, as %281+-++2sqrt%285%29%29+%2B+%281+%2B+2sqrt%285%29%29+=+2.
The product of the roots must be -3/2. This is not true, as %281+-++2sqrt%285%29%29%2A%281+%2B+2sqrt%285%29%29+=+1+-+4%2A5+=+-19.
Hence the root that you got is incorrect.