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Evaluate the expression

Evaluate the expression (-1-2i)/(8i) and write the results in the form a+bi
the real number a equals=
the real number b equals=
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3 Answers

(-1 - 2i)/(8i)
Multiply by i/i
(-i + 2)/(-8)
(-2 + i)/8
-1/4 + 1/8 i
Hi Dalia,
multiply the numerator and denominator by (0-8i)
          =(8i+16i²)/-64i²   (i²=-1)
a=-1/4  and  b=1/8
When you are dividing, you can not have an imaginary number in the denominator (bottom of the fraction), just like you cannot have a radical in the denominator. To get rid of it, you multiply both the top and the bottom by 8i so you will get:
{(-1 - 2i)(8i)}/{(8i)(8i)}
On the top you must distribute the 8i so you get -8i -16i2. Since iis really -1, you get -8i - (-16) which is -8i +16, or in a + bi format, 16 -8i. 
On the bottom you get 64iand again, since iis -1, you get -64. 
This leaves you with (16 -8i)/-64.
Since all of these terms have a common factor, we can factor out a -8. When we do this we get:
(-2 + i)/8
in a + bi format this would be -2/8 + i/8 where the first fraction can again be reduced to -1/4.
This would mean a = -1/4 and b= 1/8