So firstly we take the coefficient in front of n^2 and multiply by the constant (5x7) to get 35. Then we have to find two numbers that multiply to 35 but when added they equal our single n value (2) for this question we would have -5 and 7. In stead of 2n we have -5n and 7n.
So 5n^2-5n+7n+7 then we take out common factors between the first two numbers and between the second set of numbers. 5n(n+1) +7(n+1). Then we take the equation in the brackets and the numbers out side the brackets. (N+1) (5n+7)
