In light of this pattern, consider the choices in Example 2. The exponents in the choices are
descending multiples of 1, 2, 3, 4, and 5, respectively. Only in (D)—exponent-multiples of 4—do you
add overall values of 1 + 1 + 1 + 1 to get 4. In every other choice, you add combinations of i, –1, –i,
and 1 in varying orders. But no matter in what order you add the terms, the sum is zero.
The answer is (D).
To multiply complex numbers, use FOIL. (Review chapter 4 if you forgot what FOIL stands for. It’s
a way of remembering the order for multiplying binomials: first, outer, inner, last.) Just remember
again to take that extra step of changing i^2 to –1:
LOGIC
If you encounter a logic question on Math 2, it is likely that about all you’ll have to know is the so-
called contrapositive. That’s what Example 3 is getting at.
CONTRAPOSITIVE
“If p, then q,” is logically equivalent to “If not q, then not p.”Example 3