Roots of the equation x^2 + 2ix - 4 = 0

[SassyC]

So I am going back to college after a 10 year break and I need to take a math placement test. For the LIFE ofme I can not remember how to even start to figure this problem out:

The equation x^2 + 2ix - 4 = 0

Help! I have the answer I just need the explanation!

 

[galactus]

Just to make sure. Is that 'i' suposed to be there?. That represents complex numbers.

 

[SassyC]

Yep.

 

[galactus]

Do you remember the quadratic formula?.

\(\displaystyle \L\\\frac{-b\pm\sqrt{b^{2}-4ac}}{2a}\)

\(\displaystyle a=1, \;\ b=2i, \;\ c=-4\)

That will give you the two complex solutions.

 

[SassyC]

OK, I am still not getting the answer.

I want to show you my work but I can not find the squrt symbol!

 

[galactus]

Just type 'sqrt'. Better yet, use LaTex. Click on quote at the upper right corner of my post to see how I made the nice math type.

Anyway:

\(\displaystyle \L\\\frac{-2i\pm\sqrt{(2i)^{2}-4(1)(-4)}}{2(1)}\)

Remember that \(\displaystyle i^{2}=-1\)

Now, simplify.

 

[SassyC]

Thanks!

I forgot that \(\displaystyle i^2=-1\)