Answer sheet says 13.. I say 169. modulus of 5+12i would be 13.. and when it's squared it is 169. and i can foil it out to -119+120i which has a modulus of 169. Am I doing this right?
I find some wrong answers on answer sheets somewhat frequently. On some of the 90s tests, they would have answers to problems that are in, say, base 7 and the answer will be 74. You can't have 7 as a digit if the number is base 7
The modulus of (a + bi) is the square root of (a^2 + b^2), so you are correct - the modulus of (5 + 12i) is 13, and the modulus of (5 + 12i) ^2 is (sq root (5^2 + 12^2) )^2 or simply (5^2 + 12^2) or 13^2 or 169.
I do these in kind of a weird way, so don't yell at me too much.
Start with the ones of each the numbers. You have pluses and minuses. The idea here is to add up up each and write down the sum. So, in this case you have +5, -7, and +6. 11 - 7 is 4. Go ahead and write this down.
Next, move on to the tens. You have +6,-5, and +7. You get 13 - 5 = 8. Write this down
Finally you have the hundreds. +7,-6,+5 = 12 - 6 = 6. Write it down.
Answer: 684, BYATCH!
Try the next one now... Doing it all at once eliminates the thinking involved, which is why I'm proud to say I figured out this method all on my own. *Blows raspberry*
I find some wrong answers on answer sheets somewhat frequently. On some of the 90s tests, they would have answers to problems that are in, say, base 7 and the answer will be 74. You can't have 7 as a digit if the number is base 7 
