(c+b)(c-b)+5c^2 = c^2 - b^2 + cb + cb + 5c^2= c^2 + cb - b^2 + cb + 5c^2= c^2 + 2c*b - b^2 + 5c^2= 6c^2 + 2cb - b^2
(c+b)(c-b)+5c^2 = c^2 - b^2 + cb + cb + 5c^2
= c^2 + cb - b^2 + cb + 5c^2
= c^2 + 2c*b - b^2 + 5c^2
= 6c^2 + 2cb - b^2