Math help again because I suck at it.?

Question

(10 + 2i) + (4 - 7i)
this is what i did..
=10+2i+4-7i
=14-5i
is that right?

and then..

(4 + 3i)(2 - 5i)
i FOILed it..
and got 8 - 20i + 6i - 15i^2
and then got 8 - 14i - 15i^2

thank you soooo much!!!!

Answer 1

your addition is fine

don't forget that i^2 = -1, so you can simplify the multiplication further:

8 - 14i - 15i^2
= 8 - 14i - 15 * (-1)
= 8 - 14i + 15
= 23 - 14i

hope this helps

Answer 2

The first one is correct.

Is i an ordinary unknown, or is i = √(-1)?
(4+3i)(2-5i) = 8 - 20i + 6i - 15i²
= -15i² -14i + 8

If i is a regular unknown, then using quadratic formula,
i = (14±26)/(-30)
i₊ = -4/3
i₋ = 0.4

If i = √(-1) then
-15i² -14i + 8 = -15(-1) - 14i + 8
= 15 - 14i + 8
= 23 - 14i

Answer 3

the addition was right, but you need to finish the multiplication:

8 - 14i - 15i² =
8 - 14i - 15(-1) =
8 - 14i + 15 =
23 - 14i

Answer 4

i^2= -1 so
8-14i+15= 23 -14i

Answer 5

Well, the first one is correct. But the second one, it's 23-14i

Answer 6

I agree with your first answer.

Your second answer looks fine as far as it goes. Now just make use of the fact that i^2 = -1 to simplify it even further. (I'm assuming i means the imaginary unit in this context.)

It doesn't look like you suck at math to me...

Answer 7

the first one is right... for the second one you have to remember that i^2 is equal to -1. therefore you should be able to simplify it further.

Answer 8

First is right..and second is right too..Congrats!

Answer 9

school is for foools!

haha just playin just playin


stay in school!

Answer 10

both are right