Math problem

[OnMyOwn]

Okay, this seems basic, but there must be something I'm not understanding.

 

What is the sum of 3 + 4i and -9 - 2i?

[regentrude]

What is the sum of 3 + 4i and -9 - 2i?

 

3 + 4i +( -9 - 2i) = 3-9+ 4i-2i= -6 +2i

 

Just add all the terms and don't forget about the negatives in the second number.

you can check your answer by drawing the numbers in the complex plane and doing the addition graphically

Edited May 12, 2016 by regentrude

[Cosmos]

What are you not understanding? The real parts and the imaginary parts are added separately, so the answer is -6 + 2i.

[OnMyOwn]

Thank you! My dd is taking the aops precalculus placement test and that is the answer she got. The answer key gave -6 + 6i as the answer, so I was trying to figure out what she did wrong. It must be a problem with the key.

[Cosmos]

Are you looking at this pretest on their website?

 

Problem 2a says: The sum of 3 + 4i and -9 + 2i. And the answer to that is -6 + 6i.

 

If you got the test somewhere else and it has a typo, let AOPS know. They're good about correcting errors.

[OnMyOwn]

Are you looking at this pretest on their website?

 

Problem 2a says: The sum of 3 + 4i and -9 + 2i. And the answer to that is -6 + 6i.

 

If you got the test somewhere else and it has a typo, let AOPS know. They're good about correcting errors.

Ah, thanks! My printer is running low on toner and the plus in front of the 2i must not have fully printed because it looks like a minus. I thought there must be something more to it, which is why I asked here.

 

And sorry! Everything else on the page printed out fine, so I had no reason to suspect that it might be a printing issue.

Edited May 12, 2016 by OnMyOwn

[Cosmos]

Little things like that are annoying. It's good when you figure out the problem.

 

When I was printing out AP test sample questions a couple of weeks ago something went weird on my printer. One copy came out fine, but the second one came out missing all the math symbols. I couldn't justify wasting paper by printing again, so I had to go through by hand and mark in all the math symbols. I gave ds the good copy and myself the hand lettered one.