How do you express the product (2x-1)(3x+4) as a trinomial?
The problem of a binomial times a binomial is like multiplying a two digit number times a two digit number.
Set it up as two by two matrix.
...... 2x -1
+4 ..... +8x ......... -4
Combining the like terms of - 3x and + 8x gives +5x
So the trinomial is