Explanation for Question 13 From the Math (No Calc) Section on the Official Sat Practice Test 6
Question 13 gives us this expression. 2 Two X squared minus four, X is equal to T and then it asks 3 us in the equation above T is a constant. 4 If the equation has no real solution, which of the following could be the 5 value of T. So we're trying to see which of these answer choices 6 we could plug in for tea, and there would be no solution. 7 It's a picture of this graphically to hopefully make it a little easier to 8 understand. What's being asked, 9 we've got two X squared minus four X. So that's some parabola somewhere in 10 space. We don't know where it is on the X, Y plane. 11 We're trying to find a value of T a constant such that it's essentially 12 a straight line and these two graphs wouldn't intersect. 13 So if there was a solution, it might look like this. 14 They'd cross here and here, but we want a scenario in which there is 15 no solution. So it is underneath it, 16 essentially assuming that the parabola curves upward or it's above it, 17 if the Preble occurs downward. 18 All right. So the way that we're going to solve this is by evaluating 19 the discriminant and the discriminant of a parabolic function 20 is going to be B squared minus four AC, 21 let's reorder this to make it clear what we're doing and how this resembles 22 a quadratic function. So we have two X minus 23 four X, and we can move the T over to the other side. 24 So minus T is equal to zero. 25 Our aim is to our B is negative four and our C is negative 26 T. So it's evaluate that discriminant....