The product of a complex number and 4i is 4i-12. Find the missing complex number.?

Question

Krishnamurthy · Answer

The missing complex number is 1 + 3i.

Puzzling · Answer

Assume the number is a + bi:
4i(a + bi)
= 4ai + 4bi²
= (4a)i + 4b(-1)
= (4a)i - 4b

Now compare that to the product you got:
4a = 4 --> a = 1
-4b = -12 --> b = 3

Answer:
1 + 3i

az_lender · Answer

It must be 1 + 3i.

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