I might not be the brightest bob in the bunch but I am having trouble with a simple quadratic equation. k^2 + (k + 4)^2 = 346 According to my manual expands to: k^2 + k^2 + 8k + 16 = 346 Everything is going fine until I see the 8k. Where did the 8k come from? Or is my manual wrong? If anyone is willing to aid a poor soul with his maths I would be very grateful.