Math
posted by Anonymous .
1)AP has U6=12.5 and U19=32
a+5d=12.5 (&)
a+18d=32 (2)
(2)(1), d=1.5
therefore, a=5
(a)What is the nth term?Tn=5+(n1)1.5
(b)What is the sum of 4 terms between U10 and U13 inclusive?
2)Un=1/2^n3
(a)What is the nature of this sequence?
(b)Calculate the sum of the first nine terms?
3)Un=120.5n
(a)Solve SUMn=0
(b)If Wm=2+5m, when is Wm first a three digit number?
(c)Find m for the case where Wm=U10

Math 
Reiny
for 1. a) I would simplify a bit further.
Tn=5+(n1)1.5
= 5 + 1.5 n  1.5
= 1.5n + 3.5
for b)
find the sum of the first 13 terms, then
find the sum of the first 9 terms.
2. Clearly a geometric sequence if the expression is (1/2)^(n3)
The problem is that you did not specify the starting value of n
e.g. if you start with n = 4, term 1 is 1/2
if you start with n = 1 then the first term is 4
In any case r = 1/2
Use you sum formula to find the sum of 9 terms.
3. obviously an arithmetic sequence with a= 11.5 , d= .5
Sum(n) = n/2[2a + (n1)d]
0 = n/2[23  .5(n1)]
solve for n
Respond to this Question
Similar Questions

9th grade math honors
suppose t(1)=91 and 67 is another term of an arithmetic sequence, with. What is the equation of the nth term of the sequence if there are n terms between these two? 
algebra 2
The first 3 terms in a geometric sequence are 1.1, 1.65, and 2.475. Part A: What is the sum of the first 6 terms of the sequence? 
algebra 2 help please/check
The first 3 terms in a geometric sequence are 1.1, 1.65, and 2.475. Part A: What is the sum of the first 6 terms of the sequence? 
Algebra II
The first 3 terms in a geometric sequence are 1.1, 1.65, and 2.475. Part A: What is the sum of the first 6 terms of the sequence? 
Math ( Can You check my Work?)
1.an = 3n  1 2. an = 2(2n  3) 3.an = 4^n 4.an = (2/3)^n 5. an = (1)^n(n + 5) 6. an = (1)^n + 1(n + 6) 7. an= n+3/2n1 8. a1 = 5 and an = an1  3 for n ≥ 2 9. a1 = 6 and an = 2an1 for n ≥ 2 10.a1 = 4 and an = 3an1 … 
Maths
Hi, I am working on some Nth problems  can anyone tell me if this is correct : Nth term sequence is n + 4 are the first three terms 5,6,7, A nth term is 85  5n are the first three terms of the sequence 17, 34, 51, A nth term is … 
Mathematics
Deternine the formula of the nth term of the sequence if the sum of the second and sixth terms of an arithmetic sequence is 4.the third term is 24 more than the leventh tern 
mathssequence need help
if the sequence is 2,15,52,125,246.... find the nth term expression and sum of the nth terms 
maths sequence
if the sequence is 2,15,52,125,246.... find the nth term expression and sum of the nth terms 
Maths
The first 5 terms of an arithmetic sequence are: 7 13 19 25 31 Prove that the difference between the squares of any two terms of the sequence is always a multiple of 24 Nth term = ?