## tvise b^2+16b+1=0 is the answer b=8+3root7? one year ago one year ago

1. mathslover

$\large{x=\frac{-b \pm \sqrt{b^2-4ac}}{2a}}$ are you sure that you applied this formula?

2. tvise

It says complete the square do i still do the quadratic formula?

If requests that you complete the square, you should do so. I think you have it almost whipped, check your signs.

4. tvise

ahh it should be a - 8

5. mathslover

no if it says complete the square then : $\large{b^2+16b+1=0}$ $\large{b^2+16b+1+64=0+64}$ $\large{(b+8)^2 = 63}$ $\large{b = \sqrt{63} -8}$

I came up with:$-8\pm3\sqrt{7}$

7. mathslover

$\large{b = -8 \pm \sqrt{63}}$ $\large{b = -8 \pm 3\sqrt{7}}$

Note that $\sqrt{63}=\sqrt{9}\sqrt{7}$

9. mathslover

got it @tvise ?

10. tvise

Yes. When i originally did it i did not isolate the variable so when i re did it i forgot to change signs

11. mathslover

no problem, take care of it from now, :)