Question

Question will be below, I think I have the answer, but am not 100% sure..

Answer 1

When added, what is the simplified form of \[\left( 6+\sqrt{-4} \right)+\left( -15-\sqrt{-25} \right)\]? Write the answer in standard form, a + bi, where a and b are real numbers.

Answer 2

The answer choices are
A)-9-3i
B)9-isqrt21
C)9+7i
D)-9+7i

Answer 3

@FearBigJJRob
The best way is to post your answer for a check.

Answer 4

@mhchen that is 1-21i ? I believe? the answer I believe it to be is either A or D, but am not sure how to finish the ending off

Answer 5

I think it goes with the original equation becoming -9 I know for sure as the first, but what do I do with the negative square roots? My lesson is not telling me this..would I substitute a -2 in for sqrt-4 and a -5 for sqrt-25? @mhchen

Answer 6

@FearBigJJRob
I believe it is much faster to multiply it out (FOIL) and simplifying than to make guesses to the answers.

Answer 7

Mathmate I did it how me lesson and the help video gave me, however they never showed us how to work with the -sqrt numbers... I think I have seen it somewhere before but I forgot, thats what I needed help on

Answer 8

@mathmale do you know how to work this out? but for the equation\[\left( 7+\sqrt{-16} \right)=\left( -3-\sqrt{-36} \right)\] can you help me with this? either by showing me how to fully work this equation out or the same one with different numbers please? Im stuck.

Answer 9

@whpalmer4 can you help me?

Answer 10

\(\sqrt{-5}=\sqrt{-1\times 5}=\sqrt{-1}\times\sqrt{5}=\sqrt{5}i\) where \(i=\sqrt{-1}\)
so
\(\left( 6+\sqrt{-4} \right)+\left( -15-\sqrt{-25} \right)\)
=\(\left( 6+\sqrt{4}i \right)+\left( -15-\sqrt{25}i \right)\)
=\(\left( 6+2i \right)+\left( -15-5i \right)\)
= ...
I'll let you finish the sum.

Answer 11

-9-3i thanks @mathmate now that I know sqrt of a negative number is just sqrt of that number plus i, thank you

Answer 12

You're welcome! :)