Write (21 − 4i) − (16 + 7i) + 28i as a complex number in standard form.
(21 − 4i) − (16 + 7i) + 28i
just like basic algebra ...
= 21 - 4i - 16 - 7i + 28i
= 5 + 17i
To simplify the expression, let's combine like terms.
We have: (21 - 4i) - (16 + 7i) + 28i.
First, let's deal with the real numbers (the numbers without the "i" term):
21 - 16 = 5 (subtracting 16 from 21)
Now let's deal with the imaginary numbers (the numbers with the "i" term):
-4i - 7i + 28i = 17i (adding -4i, -7i, and 28i)
Now we can combine the real number and the imaginary number to get the final answer:
5 + 17i.
Therefore, (21 - 4i) - (16 + 7i) + 28i can be expressed as the complex number 5 + 17i in standard form.