I think it must have a power like squared or cubed also I think it must have a subtraction sign... Some examples of difference of two squares: 9x^2 - 1 Which would be = (3x+1) (3x-1) 4n^2 - 49 Which would be = (2n-7) (2n+7) 249r^2 - 150 Which would be = 6(7r+5) (7r-5) 150k^2 - 216 Which would be = 6(5k+6) (5k-6) Notice that each bracket for each answer, one bracket has a + sign and another has a - sign.