dellzasaur Group Title Can someone please check my work?? Wanna make sure I'm doing this right! Simply each number by using the imaginary number i. thanks! one year ago one year ago

1. dellzasaur Group Title

$\sqrt{-7}$ = 7i or $i \sqrt{7}$

2. dellzasaur Group Title

$\sqrt{-81}$ = 3i

3. dellzasaur Group Title

$\sqrt{-16}$ = $2i \sqrt{4}$

4. dellzasaur Group Title

$3\sqrt{-9}$ = $3i$

5. Dido525 Group Title

The last one is wrong.

6. dellzasaur Group Title

@dido525 Oh wow!! Thank you. I can't believe I'm doing these somewhat right lol. Would it be $3i \sqrt{3}$ ?? And there was also a problem that was $\sqrt{-72}$ I got: $2i \sqrt{3}$

7. Dido525 Group Title

The last one should be 9i.

8. Dido525 Group Title

Well think about it WITHOUT the negative.

9. Dido525 Group Title

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10. Dido525 Group Title

|dw:1352593754329:dw|

11. Dido525 Group Title

Now what would you do?

12. dellzasaur Group Title

is that a 4 and 18? I would think to factor them to 2 x 2 and 9 x 2 maybe

13. dellzasaur Group Title

14. dellzasaur Group Title

|dw:1352593862710:dw|

15. dellzasaur Group Title

@Dido525

16. Dido525 Group Title

No No.

17. Dido525 Group Title

|dw:1352594047004:dw|

18. dellzasaur Group Title

@Dido525 Oh ok! That made since. I was using 8, 9, and i to make -72

19. Dido525 Group Title

Okay :) .

20. dellzasaur Group Title

@Dido525 Thank you so much for all your help :) Makes me feel more confident about simplying them!

21. dellzasaur Group Title

*simplifying whoops

22. Zarkon Group Title

$\sqrt{-72}=\sqrt{(-1)\cdot2\cdot 36}$ $=6i\sqrt{2}$

23. Dido525 Group Title

Okay that works too.

24. chaguanas Group Title

Getting the i right, but need to look at $\sqrt{81} and \sqrt{16}$

25. dellzasaur Group Title

@chaguanas Would I do $3i \sqrt{3}$ for -81? and 4i or $4i \sqrt{4}$ for -16?

26. Zarkon Group Title

do you know what $$\sqrt{81}$$is?

27. dellzasaur Group Title

@Zarkon 9

28. Zarkon Group Title

well...$\sqrt{-81}=\sqrt{(-1)81}=i9=9i$

29. dellzasaur Group Title

@Zarkon Ohh so that's how you do it. You wouldn't factor the 9 out to a 3?

30. Zarkon Group Title

no

31. Zarkon Group Title

for any $$a>0$$ $\sqrt{-a^2}=a\cdot i$ so $\sqrt{-81}=\sqrt{-9^2}=9i$

32. Zarkon Group Title

$\sqrt{-16}=\sqrt{-4^2}=4i$

33. dellzasaur Group Title

@Zarkon Oh alright! I'm not sure if my teacher taught me about the a>0 thing but that makes sense. Thank you very much :) Explained a lot.