(5 - 3i)(2 + 4i)

Question

Write the expression as a complex number in standard form

Answer 1

You can use the FOIL (first, outside, inside, last) method & simplification to get to standard form.

This turns it into:

(5 - 3i)(2 + 4i) = 5(2) + 5(4i) - 3i(2) - 3i(4i)

Then, we multiply it out and simplify:

10 + 20i - 6i - 12i² = -12i² + 14i + 10

Since i = sqrt(-1), i²= -1. Then we can simplify further:

-12(-1) + 14i + 10 = 12 + 14i + 10

Thus, we end up with the standard form:

22 + 14i

Answer 2