Explanation for Question 20 From the Math (No Calc) Section on the 2018 May Sat
Question 20 says in the equation above a and B are real numbers 2 and I is equal to root negative one. 3 What is the value of a, and I've also written here because I's equal 4 to root negative one. We know that I squared is just equal to negative 5 one. So I've rewritten the problem down here and we're going to start by 6 distributing. So 15 times six is equal to 90. 7 That's going to be plus negative 45. 8 I plus negative 24. 9 I plus 12 I 10 squared is equal to a plus the I, 11 and I'm going to replace, I squared with negative one. 12 So we can rewrite this as 90 plus add 45 13 and 24. That becomes 40, 50, 60 negative 69. 14 I plus negative 12. 15 Or if you just subtract 12 from 90, 78 16 plus negative 69, 17 I is equal to a plus B 18 I, and they want to know what the value of a is. 19 And the value of a is the number that doesn't have an ILX to 20 it. So the answer is just 78.