## anonymous 4 years ago Could somebody please help me study for a pre-algebra test? I have some questions.

1. slaaibak

2. anonymous

Okay thanks! I really appreciate it.

3. anonymous

Okay. sooo, this is really broad, but I don't understand negative exponents.... At all.

4. Akshay_Budhkar

So you got some specific questions or do you want me or us to explain you negative exponents from scratch?

5. anonymous

Ummmmmmm. Why does a negative exponent make a fraction? I don't understand the basic concept.

6. slaaibak

Negative exponents simply means this: $a^{-x} = {1 \over a^x}$

7. Akshay_Budhkar

yea slaaibak got it

8. anonymous

Yes but why are they defined that way?

9. Akshay_Budhkar

it is simple

10. Akshay_Budhkar

do you know $a^x \times a^y= a^{x+y}$

11. anonymous

No.

12. Akshay_Budhkar

now say we want $a^x \times a^y = 1$

13. anonymous

Well yeah I do sorry.

14. anonymous

Okay.

15. anonymous

You'd made one negative!!! AHHH I GET IT!

16. Akshay_Budhkar

so when we solve that we get $a^{x+y}= 1 = a^0$

17. Akshay_Budhkar

thats good! You get it :D

18. anonymous

Teehee! Wow that just clicked. My math teacher didn't explain it that way.......

19. Akshay_Budhkar

its my pleasure helping you click it :D

20. anonymous

So another thing, how do you deal with #s with exponents in a fraction?

21. slaaibak

22. anonymous

Ummmm. How do you make fractions with this equation thing?

23. slaaibak

type over

24. anonymous

...

25. Akshay_Budhkar

3 over 4 $3 \over 4$

26. slaaibak

Use this code: {1 over 2} would be ${1 \over 2}$

27. anonymous

... Um can I just say it?

28. Akshay_Budhkar

yea what is your doubt? i do not comprehend it

29. slaaibak

yeah sure

30. anonymous

Okay so if you had y^-5 times 2^3 over y^4 times x^2.

31. anonymous

Or something to that effect.

32. Akshay_Budhkar

$y^-5 \times 2^3 \over y^4 \times x^2.$

33. slaaibak

${ y^{-5} * 2^3 \over y^4 * x^2}$

34. Akshay_Budhkar

35. anonymous

Lol yeah.

36. slaaibak

You're faster than me xD

37. Akshay_Budhkar

i am not lol

38. anonymous

=.=

39. anonymous

?

40. slaaibak

If there's multiplication, you can take y^-5 and but it below the line, $y^{-5} = {1 \over y^5}$ You can immediately write 2^3 as 8. So now you have: ${1 \over y^5} * {8 \over x^2 * y^4}$

41. slaaibak

put*, not but

42. slaaibak

Then, you can multiply similar variables with eachother and add the powers. it becomes: $8 \over y^9 * x^2$

43. anonymous

44. Akshay_Budhkar

45. slaaibak

I made a spelling mistake in my post.

46. anonymous

Yeah but how did you get y^9?

47. anonymous

I know you have to add... Or subtract the exponents or something.

48. slaaibak

$y^4 * y^5 = y^{5 + 4}$

49. anonymous

OH okay.

50. Akshay_Budhkar

the main aim of such questions is to convert your negative exponents into positive by taking its reciprocal

51. anonymous

Um one more thing. How would you get {1 over 9} % of 90. Or something like that.

52. anonymous

Aw shoot. I messed up the thing.

53. anonymous

${1 \over 9}$

54. Akshay_Budhkar

percent is always divided by 100

55. anonymous

Yes.

56. Akshay_Budhkar

so 1/9 percent is $(1/9 ) \over 100 = 1\over900$

57. Akshay_Budhkar

1/900

58. anonymous

Sure...

59. Akshay_Budhkar

of 90 is 1/900 of 90.. of implies multiplication

60. Akshay_Budhkar

so it is 1/900 times 90 = 90/900 = 1/10

61. anonymous

Yes yes I get it.

62. anonymous

That makes sense! Okay that's all! And I have to go. Thank you so much. ^.^

63. Akshay_Budhkar

it is my pleasure