Expanding using distributive property

 

 

In this example we have (2a + 5) (a^2 – 7a – 9) which will eventually equal 2a^3 – 9a^2 – 53a -45, in this box method we have to split up the binomial and trinomial into a 2×3 rectangle and multiply so (2a x a^2) , (2a x -7) , (2a x -9) , (5 x a^2) , (5 x -7) , (5 x -9) and we fill in the rectangle with the answers and then simplify the zero pairs and then we put the terms in order of degree which equals 2a^3 -9a^2 – 53a -45