Explanation for Question 15 From the Math (No Calc) Section on the Official Sat Practice Test 4
Now we're looking at number 15, which gives us a quadratic equation and tells 2 us that X and P are constants. And so you'll see the sat, 3 throw this word constant around a lot. 4 Um, constant just basically means a normal number and also that it 5 doesn't change. 6 Um, and so you might see this around sometimes as well, 7 a triangle, which is really, um, Delta means change. 8 Uh, I'll use that pretty often when I write my explanations. 9 Um, but what this means here is that K and P they're just normal 10 numbers like negative ones, zero to any number. 11 Um, and that they're always going to be the same. So if K is 12 one K is always one, no matter what value X is. 13 And so right now we're going to solve for the solutions for X. 14 And so what I want you to see here is the format of our 15 answer choices, right? 16 Usually when you see solve for solutions, what pops into people's minds is factor, 17 but we see a plus or minus side, and that should be really reminiscent 18 of the quadratic equation, which has a form X equals opposite B 19 plus or minus, right square root. 20 There's a square root B squared minus four, 21 AC all over to a, 22 so really we're just going to solve this by plugging into the quadratic equation. 23 Uh, so let's start by looking at this here, 24 right? And we want to get everything off to one side because we know 25 it's a X squared plus BX plus C is equal to zero. 26 And right now we're not equal to zero. We're equal to two P. 27 So we can fix that...