Remark
What is messing you up is the definition of a, b and c.
The general equation for a quadratic is
y = ax^2 + bx + c
a is the number in front of x^2. You seem to understand that.
b is the number in front of x.
c is the number that has no x associated with it.
Step One
Find ac
a = 1 ; c= 14. ac = 1*14 =14
Step Two
1 * 14 = c 1 + 14 = 15. That is not the value for b. The only other two you can try is 2 and 7
2 * 7 = 14 2 + 7 = 9 which does equal b. To put it in the terms of the question 2 + 7 = b = 9
Step 3
x^2 + 2x + 7x + 14
Step 4
1(x^2 + 2x) + 1(7x + 14)
x(x + 2) + 7(x + 2)
Step 5
The gcf is (x + 2) Pull it out as a common factor.
(x + 2)(x +7)