r^2 + 6r + -8 = 0

-8 -8

= r^2 + 6r = -8 + 9

(r+3)^2 = 1

I am stuck and the book has my answers to be -2 and -4

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- Mar 20th 2011, 07:58 AMtoniefactor to solve the equation
r^2 + 6r + -8 = 0

-8 -8

= r^2 + 6r = -8 + 9

(r+3)^2 = 1

I am stuck and the book has my answers to be -2 and -4 - Mar 20th 2011, 08:10 AMskeeter
- Mar 20th 2011, 08:12 AMe^(i*pi)
You're completing the square rather than factoring. Factoring is finding out which values of and satisfy the equation

Your syntax is confusing, I have assumed the constant term is positive (+8) because that factors.

What two numbers multiply to give +8 and sum to +6 - Mar 20th 2011, 08:35 AMtonie
While thank you so much, you fully understand my issue even though my syntax was confusing. That is exactly what the book had for the problem and answer!

- Mar 20th 2011, 08:05 PMProve It
If you wish to factorise by completing the square, and assuming that your originally equation is ...

. - Mar 21st 2011, 05:28 AMHallsofIvy
Or, after you have , as in your first post, just take the square root of both sides:

[math\]r+ 3= \pm 1[/tex] so that .

Taking the "+" sign, and taking the "-" sign, .