See the pattern? This repeats ad infinitum, every four integer powers. This
comes in handy in problems that involve complex numbers, which combine real
and imaginary numbers in single expressions.
What is (3i + 4) (5 – 6i^3 )?
First, we FOIL this like a standard algebra problem:
15 i – 18i^4 + 20 – 24i^3
Next, we check in on our i values. That regular i stays the same (because i^1 =
i), the i^4 becomes 1, and the i^3 becomes –i. Let’s rewrite it:
15 i – 18(1) + 20 – 24(–i)
15 i – 18 + 20 + 24i
2 + 39i
GRID-IN PROBLEMS
Unlike all other questions on the SAT, grid-in problems allow you to produce
your own answer. Finally, a chance to express yourself!