How do you evaluate (\frac { 1} { 1- 2i } + \frac { 3} { 1+ i } ) ( \frac { 3+ 4i } { 2- 4i } ) (112i+31+i)(3+4i24i)?

1 Answer
Nov 29, 2017

(22+i)/(2-14i)22+i214i

Explanation:

1/(1 - 2i) + 3/(1 + i) = ((1 + i) + 3(1 - 2i))/((1 - 2i)(1 + i))112i+31+i=(1+i)+3(12i)(12i)(1+i) (common denominator)
=(1 + i + 3 - 6i)/(1 + i - 2i + 2)=1+i+36i1+i2i+2
=(4 - 5i)/(3 - i)=45i3i

Now, we take that answer and multiply it by (3+4i)/(2-4i)3+4i24i.

((4-5i)/(3-i))((3+4i)/(2-4i)) = ((4-5i)(3+4i))/((3-i)(2-4i))(45i3i)(3+4i24i)=(45i)(3+4i)(3i)(24i)
=(12 + 16i - 15i - 20i^2)/(6 - 12i - 2i + 4i^2)=12+16i15i20i2612i2i+4i2
=(12 + 16i - 15i + 20)/(6 - 12i - 2i - 4)=12+16i15i+20612i2i4 (since i^2 = 1i2=1)
=(22 + i)/(2 - 14i)=22+i214i (by simplifying)