The common factor of 16 is <span> 1, 2, 4, 5, 8, 10, 20 and 40. the common factor of 20 is </span><span>1, 2, 3, 4, 5, 6, 8, 10, 12, 15, 20, 24, 30, 40, 60, 120. </span>
The line of symmetry is the center/ middle of the parabola where the curve shifts. Since the line of symmetry is at x=2 and the zero is at x= -1, you have the find the difference between the values which is 3. So the other zero is three the right of the line of symmetry at x= 5.