Explanation for Question 28 From the Math (Calc) Section on the Official Sat Practice Test 4
Not for question number 28, we're trying to find any equivalent form. 2 So essentially we're trying to rewrite this equation right here of F of X 3 in which the minimum value appears as a constant or coefficient. 4 So if we want to be able to see the minimum value is a 5 constant, we need to write our equation of this parabola. 6 We know it's a parabola because it's set up so we can see the 7 zeros here, right. And if we were to factor it out, 8 we would get something like X squared, plus two X minus 24. 9 Um, but we want the minimum value is that means we need to write 10 it in vertex form. 11 So we should immediately eliminate any answer choice that is not in vertex form, 12 which is B, B as in standard form, 13 but answer choices like, um, C and D are easily 14 in vertex form. 15 And similarly a is also not in vertex form because vertex form has, 16 um, in its general form X minus H squared plus K, 17 where K is actually going to be your minimum slash maximum value, 18 depending on whether it's an upward parabola, it has a minimum, 19 or it's a downward parabola. It has a maximum. 20 Um, and so in this case, 21 right, the question is, where is our minimum? 22 Is it at, you know, positive one, 23 negative 21? Or is it at negative one, 24 negative 25? And so the reason that I looked at this, 25 it says minus one, and I said that that would be positive. 26 One is because when you look at the general forum, 27 we have minus H right? 28 And so that H is actually the X coordinat...