## anonymous 3 years ago Write the explicit formula for the geometric sequence. a1 = -5 a2 = 20 a3 = -80 A. an = -5 • (-4)n B. an = -5(-4)n-1 C. an = -4(-5)n-1 D. an = -5 • (4)n

1. bahrom7893

look a1 = -5 n=1 a2=20 n=2, etc..

2. anonymous

It would be B because in a geometric sequence, you have $\large ar ^{n-1}$ and in finding our r, we take $$\large\frac{ a _{2} }{ a _{1} }$$ and that is -4

3. bahrom7893

This way you can eliminate A because term 2 doesn't match up... And I think Jhanny's right

4. anonymous

thanks you that was heard

5. anonymous

So we have a1 = -5, our r = -4 and plug it into our formula $\large ar ^{n-1}$

6. anonymous

thanks bahrom :)

7. anonymous

Can you help me with another

8. anonymous

sure

9. anonymous

What is the simplified form of the expression?|dw:1369539526178:dw|

10. anonymous

Alright, for this one you have a variable with two different powers dividing eachother, and in this case, we can simply do this. $\large \frac{ 1 }{ q ^{\color{red}{(33/4)-8} }}$

11. anonymous

we you know to solve $\color{fuchsia}{\frac{ 33 }{ 4 }}-\color{green}{8}$

12. anonymous

|dw:1369539985575:dw|

13. anonymous

That is the choices

14. anonymous

hmm...something seems wrong here.

15. anonymous

$\frac{ 33 }{ 4 }-8*(\frac{ \color{green}{4} }{ \color{green}{4} })= \frac{ 33 }{ 4 }-\frac{ \color{darkorchid}{32} }{ \color{darkorchid}{4} }$

16. anonymous

Ohh I see. hm, well what do you get when you reduce 33/4- 32/4? :D

17. anonymous

I am confused

18. anonymous

hm?

19. anonymous

I have no Idea what the answer is

20. anonymous

solve (33/4)-(32/4) and we'll work from there, you'; get your answer, promise :)

21. anonymous

I am the parent of 2 children that is failing

22. anonymous

this looks like greek to me..

23. anonymous

ok, what is.... 3-2?

24. anonymous

1

25. anonymous

good :) so 33-32 works the same way, it is also 1.

26. anonymous

So we now have $\frac{ 1 }{ q ^{\color{blue}{1/4}} }$

27. anonymous

o ok

28. anonymous

I thank you so much

29. anonymous

algebra has always been my worst subject

30. anonymous

It'll get better with practice :) Practice makes people perfect in math ^_^

31. anonymous

I remember hearing that when I was young

32. anonymous

I have another quesiton if you are up to it?

33. anonymous

Of course :) Math is a lot about understanding a problem as a whole and finding a relation to a technique method in solving, it's all patterns.

34. anonymous

sure thing

35. anonymous

I have 2 test to give to my children for the summer to help them prepare for summer school that is why I am getting the answers so I will be able to help them

36. anonymous

Interesting

37. anonymous

What is the simplified form of the expression?|dw:1369541274406:dw|

38. anonymous

$\large (3x ^{\color{forestgreen}{7/2}})^{\color{blue}{6}}(x ^{\color{green}{2}})^{\color{blue}{6}}$ here, we will start 1 part at a time. lets start with $$\large (3x ^{7/2})^{6}$$

39. anonymous

ok what do we do next

40. anonymous

we're going to multiply 6 to the 3 AND the x^(7/2)

41. anonymous

Are you able to do that?

42. anonymous

18 x

43. anonymous

I suck

44. anonymous

Hm.. not exactly, we have $\large(3^{\color{blue}{6}})(x ^{\color{blue}{(7/2)(6)}})$ which gives us $\large(729x ^{21})$

45. anonymous

A. 729x33 B. 3x33 C. 729x29 D. 3x29

46. anonymous

Now that we've taken care of the first part, we can move onto the second part, which is $\large (x ^{2})^{6} = x ^{\color{red}{6*2}}= x ^{\color{blue}{12}}$

47. anonymous

ok

48. anonymous

Now we can combine both parts together so we get $\large (729x {^\color{green}{21}}) *(x ^{\color{green}{12}}) = 729x ^{\color{red}{21+12}}$

49. anonymous

50. anonymous

Good luck with your other problems!

51. anonymous

33

52. anonymous

729x^33

53. anonymous

am I right?

54. anonymous

thanks so much