SOLUTION: given the following two complex numbers, a=3+7i and b=-2-2i,calculate the following a+b a-b a*b a/b

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Question 100060: given the following two complex numbers, a=3+7i and b=-2-2i,calculate the following
a+b
a-b
a*b
a/b

Found 2 solutions by edjones, timmy1729:
Answer by edjones(8007) About Me  (Show Source):
You can put this solution on YOUR website!
a=3+7i b=-2-2i
.
a+b
3+7i+(-2-2i)
3+7i-2-2i
group like terms: (3-2)+(7i-2i)
1+5i Ans.
.
a-b
3+7i-(-2-2i)
3+7i+2+2i
(3+2)+(7i+2i)
5+9i Ans
.
a*b
(3+7i)*(-2-2i)
-6-20i-14i^2
-6-20i+14
8-20i Ans
.
a/b
Here it gets a little tricky.
(3+7i)/(-2-2i)
multiply the top and bottom by complex congugate of the denominator:%28%283%2B7i%29%2F%28-2-2i%29%29%2A%28%28-2%2B2i%29%2F%28-2%2B2i%29%29
%28-6-8i%2B14i%5E2%29%2F%284-4i%5E2%29
%28-6-8i-14%29%2F8
%28-20-8i%29%2F8
-5%2F2-i Ans.
Ed

Answer by timmy1729(23) About Me  (Show Source):
You can put this solution on YOUR website!
given the following two complex numbers, a=3+7i and b=-2-2i,calculate the following
a+b
a-b
a*b
a/b
Ok, for the most part, treat i like a variable. a+%2B+b+=+3+%2B+7i+-2+-+2i
3+%2B+7i+-2+-+2i+=+1%2B5i
a+-+b+=+3+%2B+7i+-%28-2+-+2i%29+=+3+%2B+7i+%2B+2+%2B+2i+=+5+%2B+9i
a*b is just simply: %283%2B7i%29%28-2-2i%29+=+-6+-+6i+-+14i+-+14i%5E2
Remember that i^2 = -1. So we simplify into: -6+-+20i+%2B+14+=+8+-+20i
a/b is %283%2B7i%29%2F%28-2-2i%29
To simplify, you multiply the numerator and denominator by the denominator's complex conjugate which is -2+2i.
%28%283%2B7i%29%28-2%2B2i%29%29%2F%28%28-2-2i%29%28-2%2B2i%29%29
%28-6%2B6i-14i-14%29%2F%284+-4i+%2B+4i+%2B4%29
%28-20-8i%29%2F%288%29
%284%28-5-2i%29%29%2F%288%29
%28-5-2i%29%2F2