1) think of the last number as the PRODUCT of the polynomial. Think of the factors that go into it (when there is no number in front of the x^2, ie the letter (a) in front of the x^2 = 1 (ax^2 +bx +c where a, b, and c are numbers). The only factors of 7 are (1 and 7).
2) the rest is figuring out positive/negative of the factors, if the (b) is negative and the (c) is positive, then both of the factors will have negative numbers (remember.
(x+1) (x-7) will equal the FOIL (first, outside, inside, last). - the -7x +1x equals the -6x you need.
The way to solve this is to ask yourself the question:
What two factors have a sum of -6 (the coef of the x term) and a product of -7 (the coef of the constant) ...
After a little thought you will realize that 1 * -7 = -7 and 1 + -7 = -6
... Let me know if you need any more help.