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Answer:
C) -1 +21i
Step-by-step explanation:
For many purposes, "i" can be treated as though it is a variable. Collect terms in the usual way.
(-2 +12i) -(-1 -9i) . . . . given
= -2 +12i +1 +9i . . . . use the distributive property to eliminate parentheses
= (-2+1) +(12i +9i) . . . group like terms
= -1 +21i
