Explanation for Question 16 From the Math (Calc) Section on the Official Sat Practice Test 9
Question 16 gives us this expression and asks and the expression above 2 a is a constant. If the expression is equivalent to be X, 3 where B is a constant, what is the value of B? 4 So for this one, I've wrote up this expression right here, 5 and we know that it's going to be equivalent to be X, 6 which means that you can set it equal to be X. 7 This might be a little intimidating at first. 8 Um, how you're going to do it is you're going to group by like 9 powers and that'll will become more clear as we foil it through. 10 So one strategy for this problem is if things are looking a little confusing 11 and see if you can simplify the expression a little bit, 12 and then if it becomes any clearer at that point. 13 So let's do just that. We're going to foil out this term right here 14 for X times, X is equal to four, 15 a X squared, four X times. 16 Negative one is minus four X, 17 four times I have X is plus four, 18 a X, and then four times negative one is minus four. 19 Then we have minus X squared, plus four is equal to B 20 X. Okay. 21 So right away we can simplify it just a little bit. 22 We see that we have a minus four and a plus four and minus 23 four, plus four is equal to zero. 24 So let's cross out those terms. And then let's group by like powers. 25 So put the X squared by the X squared and the X is by 26 the exes. So we get four, 27 a X squared minus X squared, 28 minus four X plus four, 29 a X is equal to B X. 30 And hopefully by looking at this, you can see right...