# Thread: Quadratic formula for complex roots

1. ## Quadratic formula for complex roots

This is a bit embarrassing. I am using the quadratic formula to obtain two complex roots and for the life of me I can not get the answer posted on the solution sheet. Could someone please take a look and see if I am wrong or, perhaps, the answer sheet is? Thanks much, Frostking

(3 - x) multiplied by -- (1 - x) + 8 = 0

- x^2 + 4x + 5 = 0

When I use the quadratic I get 2 +/- - i = 2 +/- i

I am suppose to get 1 +/- 2i

I know I am going to say how stupid can I be but......I do not know where I am going wrong!!!

2. Originally Posted by Frostking
This is a bit embarrassing. I am using the quadratic formula to obtain two complex roots and for the life of me I can not get the answer posted on the solution sheet. Could someone please take a look and see if I am wrong or, perhaps, the answer sheet is? Thanks much, Frostking

(3 - x) multiplied by -- (1 - x) + 8 = 0

- x^2 + 4x + 5 = 0

When I use the quadratic I get 2 +/- - i = 2 +/- i

I am suppose to get 1 +/- 2i

I know I am going to say how stupid can I be but......I do not know where I am going wrong!!!
Working backwards, if the answer is $\displaystyle x = 1\pm2i$ then the question must have been "((3 – x) multiplied by –(1 + x)) + 8 = 0". Check that you copied the question correctly.