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December 21, 2014

December 21, 2014

Posted by **Mary** on Saturday, June 27, 2009 at 10:56am.

x^2-3x-12=0

(x^2-4)=0 (x+3)=0

x^2=4 x+3+0

x=4 x=-3

Am i on the right path or just way off??

- mathematics -
**Reiny**, Saturday, June 27, 2009 at 11:15amI am assuming there is only the one equation

x^2 - 3x - 12 = 0, because what follows makes no sense

First of all your quadratic does not factor, so you will have to either use the quadratic equation formula or complete the square.

let's use the formula:

x = (3 √(9-4(1)(-12))/2

= (3 √57)/2

Use your calculator if you need a decimal equivalent.

- Mathematics -
**Mary**, Saturday, June 27, 2009 at 11:54amOk i may be dense but i dont ge tthe formula cause when i work out

3 } (9-4(1)(-12))/2

I get 60 not 57, and i dont understand how you got 9 or 4 either

- mathematics -
**Reiny**, Saturday, June 27, 2009 at 12:03pmfor any quadratic equation

ax^2 + bx + c = 0

x = (-b √(b^2 - 4ac))/(2a)

so in our case

a = 1, b = -3, and c = -12

look at the second example on this page

http://www.nipissingu.ca/calculus/tutorials/quadratics.html

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