Identify the factors of 25 and 42. The idea is to find a combination that leads to a difference of 5, the coefficient of the v term. 25 has factors 1 and 25, and 5 and 5; 42 has 1 and 42, 2 and 21, 3 and 14, 6 and 7. The coefficient 5 is a small number so it's unlikely we'll need large numbers like 25, 42 and 21. Let's go for numbers of similar size: 5 and 5, and 6 and 7 might work. Let's imagine a game between two teams. The first team is 5 and 5 and the other team is 6 and 7. So 5 plays against 6 and its partner 5 plays against 7. Play consists of the product of the opponents, so we have 5*6=30 and 5*7=35. The difference is 5. So we nearly have the answer. By the way, the reason we subtract these products is because the sign on the constant term is negative or minus, which means subtract. If it had been + we would have added the products. So we have (5v 6)(5v 7), but what signs go in the brackets? We look at the sign in front of the middle term. It's +, so this sign must be in front of the larger of 6 and 7. If it had been minus, we put minus in front of the larger number. Answer is (5v-6)(5v+7). Note that each brackets contain opponents in the game. (When doing the algebra note that 5v in the first bracket multiplies (plays) the 7 in the second bracket. Imagine a game where the players play diagonally across the playing court.)