SOLUTION: how do I solve: x2-12x +4=0. Please help. I have to use the quadratic formula, but don't know what it is

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons  -> Quadratic Equation Lesson -> SOLUTION: how do I solve: x2-12x +4=0. Please help. I have to use the quadratic formula, but don't know what it is      Log On


   

Question 112866: how do I solve: x2-12x +4=0. Please help.
I have to use the quadratic formula, but don't know what it is
Answer by solver91311(24713) About Me  (Show Source):
You can put this solution on YOUR website!
The quadratic formula is the solution to the general quadratic equation,

ax%5E2%2Bbx%2Bc=0 and it looks like this:

x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+ where a, b, and c are the coefficients on the three terms in the equation.

In your problem, x%5E2-12x%2B4=0, a=1, b=-12, and c=4. Now all we have to do is plug in the values of a, b, and c, then do the arithmetic.



x+=+%2812+%2B-+sqrt%28+144-16+%29%29%2F2+

x+=+%2812+%2B-+sqrt%28128%29%29%2F2+

x+=+%2812+%2B-+sqrt%2864%2A2%29%29%2F2+

x+=+%2812+%2B-+8%2Asqrt%282%29%29%2F2+

x+=+6+%2B-+4%2Asqrt%282%29+

So our two solutions, and there are ALWAYS two solutions to a quadratic, are:

x+=+6+%2B+4%2Asqrt%282%29+ and x+=+6+-+4%2Asqrt%282%29+

Hope that helps.
John