  # SAT MATH Question

<p>If you have the latest Official Prep Book it's on page 456. Number 15. Answer is B. For all positive integers x, let x Triangle Symbol be defined to be (x-1)(x+1). Which of the following is equal to 6 Triangle Symbol - 5 Triangle Symbol
A. 2 Triangle Symbol + 1 Triangle Symbol
B. 3 Triangle Symbol + 2 Triangle Symbol
C. 4 Triangle SYmbol + 3 Triangle Symbol
D. 5 Triangel Symbol + 4 Triangel Symbol
E. 6 Triangle Symbol + 5 Triangle Symbol</p>

<p>I don't know how to get to answer B. If someone could please explain this one in detail it would be greatly appreciated!</p>

<p>Well 6(Triangle) = 35
5(Triangle) = 24
So 6(Triangle) - 5(Triangle) = 11</p>

<p>Now just solve the answer choices:
3(Triangle) = 8
2(Triangle) = 3
3(Triangle) + 2(Triangle) = 11

<p>Now if you're having trouble deciphering the triangle symbol's meaning:
6(Triangle) = (6-1)(6+1) = (5)(7) = 35</p>

<p>Once you've solved each triangle operation, it's just simple addition or subtraction. Since we know that 6(Triangle)=35 and 5(Triangle)=24, 35-24=11. All you need to do is find the answer choice that is equal to 11. That choice is B.</p>

<p>For future reference, the Blue Book second edition has an online supplement with all answer explanations. Create a College Board account and go to "My Organizer." In the SAT section, click on "Official SAT Study Guide: 2nd Edition."</p>

<p>If you solved the question by:</p>

<p>1) Solve the equation given in the question: (6-1)(6+1) - (5-1)(5+1) = 11.
2) Solve the answer choices in the same way and check which is similar.</p>

<p>Note: to save time, you can check beginning with Choice (C) and see that the result is 15, so logically you should move to (B) because it shows smaller numbers and check it.</p>

<p>all right. I understand now. thanks!</p>