Explanation for Question 17 From the Math (No Calc) Section on the Official Sat Practice Test 9
Question 17 gives us the equation. Four X plus two is equal to four. 2 And then it says if X satisfies the equation above what is the value 3 of two X plus one? Okay. 4 So there are two ways to do this. 5 Let me show you kind of the short cut first, 6 and then we'll go over kind of a longer way to do it. So 7 we see that four X plus two is equal to four. 8 We can notice right away that two X plus one is just two, 9 this divided by two. So to find the equivalent expression to this let's 10 divide both sides by two. So we get forest fed by two is 11 two X plus one is equal to two. 12 So the value of two X plus one is equal to two. 13 Now, if that didn't make sense, we can go a little slower. 14 And the best way to do that would be by solving for X from 15 that first expression. 16 So it got four X plus two is equal to four and we can 17 subtract two from each side, we got four X is equal to two. 18 Can we get that? X is equal to two over four, which is one 19 half. And then it's asking us for the value of two X plus one. 20 So two times one half plus one is going to be equal to one 21 plus one, which is equal to two. 22 So the value of two X plus one is equal to two, 23 a common thing to note here in a really common mistake for these problems 24 is reporting the value of X rather than the value of the expression or 25 equation that they're asking you. So make a mental note of that and pay 26 attention to that when you're solving these problems.