Question

(1+2i)(5-3i) Simplify the given expression.
operations on complex numbers
please help I tried to do it but I got different answers than the multiple choice @ganeshie8

Answer 1

the choices are:
2-15i
3+2i
5-6i
11+7i

Answer 2

@JFraser @jdoe0001

Answer 3

no clue, sorry. i haven't used complex numbers in forever

Answer 4

ok

Answer 5

@amistre64 @e.mccormick

Answer 6

what did you come up with? its just a foil ....

Answer 7

i got like 3 different answers

Answer 8

well, i tried it 3 times

Answer 9

first i got 5+6i

Answer 10

then idk, then i just did it right now and im at the last step: 5-7i-6i

Answer 11

1+2i
5-3i
-----
5+10i
-3i -6i^2
-----------
5 +7i -6(-1)

Answer 12

thats not how u do it

Answer 13

thats not the FOIL method

Answer 14

.... that IS the foil method, just not the one you are used to seeing

Answer 15

with that way, ur answer will be 5+13i , and thats not in the choices

Answer 16

did u look at the choices above

Answer 17

5 +7i -6(-1) is not equal to 5+13i

Answer 18

oh wait woops.. 11 +7i

Answer 19

i cant do it that way, they didnt show it that way in the lesson so ill nvr do it that way

Answer 20

this is what i got when i just did it

Answer 21

then FOIL it using your way ...

Answer 22

the trick is in the -6i^2 that results from the Ls

Answer 23

i^2 = -1

-6i^2 = -6(-1) = 6

Answer 24

ohhh.. y is it squared

Answer 25

(1+2i)(5-3i) is what you posted to start with

Answer 26

yea i know..

Answer 27

(-3i)(2i) = -6ii = -6i^2

Answer 28

you forgot to "ii" it

Answer 29

oh ok

Answer 30

-3i * 2i is not equal to 6i

Answer 31

ok i see now

Answer 32

err, -6i that is

Answer 33

can u help with this one

Answer 34

what do you get when you add the OI parts?

Answer 35

ok i did it -5+10i+3i-6i^2

Answer 36

thats good, now

10i + 3i = 13i

so the answer will have at least a 13i in it

Answer 37

then -5+13i-6i^2

Answer 38

so 1+13i

Answer 39

can u help with this one