Sanjay graphs a quadratic function that has x-intercepts of –3 and 7. which functions could he have graphed? check all that apply. g(x) = x2 – 4x – 21 g(x) = (x – 3)(x + 7) g(x) = 3x2 – 12x – 63 g(x) = –(x + 3)(x – 7) g(x) = x2 + 4x – 21

X-intercepts are found by factoring.  Use the quadratic formula on the first since it's in standard form and you find that your x values are in fact -3 and 7.  For the second one, use the Zero Product Property that says that x - 3 = 0 or x + 7 = 0.  Therefore, x = 3 and -7.  Signs are wrong.  So not the second one.  As for the third one, if you factor out a 3, your polynomial is exactly the same as the first one which did give us the desired x values.  So the third one checks out.  If you FOIL out the first one and then apply the quadratic formula you do get x = 3 and -7. So the fourth one checks out too.  For the last one, putting it into the quadratic formula gives you x values of 3 and -7, so no to that one.  Summary:  1st, 3rd, 4th have zeros of -3 and 7; 2nd and 5th do not.