Maths help, quadratic formula

Please explain how you use the quadratic formula step-by-step and use it to solve x^2+3x-7=0

Thanks for all answers :)

First, I will state the quadratic formula: x = [ -b ± sqrt(b^2 - 4ac)] / 2a

Quadratic equations are set up like this: ax^2 + bx + c = 0

This shows that the coefficients of each term in the quadratic equation represents a letter in the quadratic formula.

Therefore, in your problem:
Write x^2 + 3x - 7 = 0 as 1x^2 + 3x -7 = 0 so that each term has a clear coefficient.

Let a = 1, b = 3, and c = -7

x = [ -3± sqrt((-3)^2 - 4(1)(-7) ] / (2(1))

x = about 1.54 or -4.54

Hope this helps!

Do you want to derive the quadratic formula or just use it?
The formula for the general quadratic ax^2 + bx + c = 0 is
x = [-b +-sqrt(b^2 - 4ac) ]/ 2a
You derive it by 'completing the square' on the original equation, which any algebra textbook will show you.
So now put in the values of a, b, c and get a = 1, b = 3, c = -7.
x = [-3 +-sqrt(9 + 28)] / 2
sqrt(37) = 6.0828
x = [-3 + 6.0828] / 2 and x = [-3 - 6.0828] / 2
x = 1.5414 and x = - 4.5414

your equation can be written as ax^2+bx+c=0 (which is general form). So for your equation a=1, b=3 and c= -7.

Now that that's out of the way we'll get to the actual formula.

-b+/- the square root of b^2-4ac divided by 2a
heres a link to give you a clear view of what it looks like: http://www.purplemath.com/modules/quadfo…

Then you would simply sub everything in: -3+/- the square root of (-3)^2 - 4(1)(-7) divided by 2(1)

then you get your answer. Sorry that this wasn't a great explanation, it's hard when you can't actualy use the formula on here.