Question

Find the product of the complex number and its conjugate. 1 + 2i Please help

Answer 1

so whats the conjugate of 1+2i
you know ?

Answer 2

I don't :/ Could you explain?

Answer 3

yes,
conjugate of a+bi is a-bi
we just flip the sign of imaginary term

Answer 4

so, what will be conjugate of 1+2i then ?

Answer 5

ohh so it would be 1-2i right?

Answer 6

yes!

Answer 7

so we take the product now
(1+2i)(1-2i)
can you foil ?
and do you know what "i" is ?

Answer 8

i can foil and is it -1?

Answer 9

-1^2? i cant remember which of the two it is

Answer 10

i^2 = -1 ok haha

Answer 11

ys

Answer 12

\(\large i =\sqrt {-1}\)

Answer 13

ok so after i foiled i got 5

Answer 14

just 5 ?
how ? show me your work ?

Answer 15

ok so (1+2i)(1-2i)
1-2i + 2i -4i^2
1-4(-1)
1+4
5

Answer 16

you are absolutely correct!
good work :)

Answer 17

Thank You!