Weegy: x^2 - 8x - 20. Find two numbers that when multiplied together equals - 20 and when added equals - 8. The larger number has to be negative because of the - 8. The other has to be positive because a positive times a negative gives you a negative. [ The numbers are - 10 and + 2. (x + 2)(x - 10). Answer. b) - 9 + 18x^2 - 21x. Rewrite in standard form. 18x^2 - 21x - 9. Factor out a 3. 3(6x^2 - 7x - 3). Factor the trinomial. 3(3x + 1)(2x - 3). Answer c) 4x^2 - 9y^2. Factor into two binomials by taking the square roots of each term. (2x - 3y)(2x + 3y) ] (More)