Question

I know that this equation should equal either -2.162 or 4.162, but whenever I try to solve it, I always come up with the exact opposite: 2.162 or -4.162. Can someone help walk me through this?

The equation is: 0=-x^2+2x+9

Answer 1

what is a, b, c on the expression??

Answer 2

a=-1

b=2

c=9

@OOOPS

Answer 3

Right now use the quadratic formula \(\large x=\frac{-b\pm\sqrt{b^2-4ac}}{2a}\)
Now plug them in:\(\large x=\frac{-2\pm\sqrt{(2)^2-4(-1)(9)}}{2(-1)}\)
Did you get this far?

Answer 4

\(
x = \Large \frac{ -b \pm \sqrt{b ^{2} - 4ac} }{ 2a } =
\frac{ -2 \pm \sqrt{2 ^{2} - 4(-1)(9)} }{ 2(-1) = } = \\ \Large
\frac{ -2 \pm 2\sqrt{10)} }{ -2 } = 1 \mp \sqrt{10} = ?
\)

Answer 5

I got it! Thank you! @venny and @aum