You can put this solution on YOUR website! If you need a detailed solution on how to factor trinomials such as this, see my three (3) recently posted Lesson Plans in algebra.com under the topic of Quadratic Equations:
"More Factoring in Living Color in Quadratic_Equations."
"Factoring Difference of Squares in Living Color in Quadratic_Equations."
"Factoring Trinomials in Living Color in Quadratic_Equations. "
To solve the current problem, start with the first times first, which is probably 3a*3a
Next look at the last term, which has to be a 16b^2. This is probably a 4b*4b.
Next, since the last term is positive, the signs must be the SAME. Since the middle term is -24ab, the signs must be NEGATIVE.