sequence and series (1 Viewer)

[bos1234]

Find the sequence and the sum of the first 4 terms

T11 = 6 and T26 = -11 1/2

http://img224.imageshack.us/img224/4348/ajl9.png

http://img224.imageshack.us/my.php?image=ajl9.png

 

[airie]

Uhh, did you write T_n=(53/3)*(-7/6)(n-1)? If it's an AP, it should've been a plus sign, instead of a multiplication sign.

Also, did the question specify that the sequence is an AP? It might have been a GP. Or maybe the textbook answer is for the sum of the first 4 terms. (I haven't done much calculation myself, only enough to say that I think your values for a and d, if it is indeed an AP, are right [oh and d=-7/6, I think you had a typo in there too] ) Check?

 

[airie]

-15d = 17 1/2
d= -7/3 ...?

Uhh, d = -7/6. Sub it back and check.

...I do think that I can do division

 

[m0ofin]

Yes, Airie's right on the d= -7/6.