Simplify (2x+3)^2 - (2x +3)(x-5). Give your answer in the form ax^2 +bx +c

Break this down into two parts.
a. Multiply out the 1st bracket, (2x+3)^2: This goes to (2x+3)(2x+3) which is equal to 4x^2 + 9 +6x+6x . Collect the like terms to get 4x^2 +12x +9.
b. Multiply out the second bracket, -(2x + 5) (x-5), placing emphasis on the minus sign in front of the bracket. Multiplying out this bracket this equals to - 2x^2 -25 +5x -10x which is simplified to -2x^2 -5x -25.
c. After finding out these two parts, add them together to get = 2x^2 +17x -16