math
posted by Ellie .
Write the arithmetic sequence 21,13,5,3... in the standard form:
a_n=
a_n=a_1+(n1)dso a_n=21+(n1)8
*a_n=1688n
why isnt this right?

You are close. You have an error:
Your step:
a_n = 21 + (n  1)  8
should be:
a_n = 21 + (n  1) * (8) 
oh yeah sorry i wrote that wrong i put 1688n but it still said my answer was wrong

a_n = 21 + (n1)*(8)
Expand that using the distributive law.
The first term, 21, is not multiplied by 8. Only the terms in parenthesis are multiplied by 8. 
i figured out what i was doing thank you so much!

You're very welcome.

arithmetic sequence
b_n=(2)^(n1)
Respond to this Question
Similar Questions

Discrete Math
Solve the recurrence relation a_n = 2a_n1 + 15a_n2, n ≥ 2, given a₀ = 1, a₁ = 1. x² + 2x  15, the distinct roots 3 and 5, so a_n = C₁(3^n) + C₂(5)^n. The initial condition gives a₀ = 1 = … 
Calculus
Find a series ∑a_n for which ∑(a_n)^2 converges but ∑a_n diverges 
Calculus
If a_n does not equal zero for any n>=1 and ∑a_n converges absolutely, then ∑ 1/a_n diverges. The series are from n=1 to infinity. I think this is true but I'm not sure. 
Calculus
If a_n>0 and a_(n+1) <= a_n, does the alternating series ∑ ((1)^(n+1)) a_n converge or diverge? 
Algebra
find the arithmetic mean A_n1_3.9, A_n+1_=7.1 
mathematical statistics
Suppose a_n∈ [0,1] and X_n is a sequence of i.i.d random variables with p.d.f : p(X_n=1)= p(X_n= 1)=0.5 . ∑_(n=1)^∞▒a_n X_n is convergent with probability 1, is ∑_(n=1)^∞▒a_n^2 convergent? 
Math Proof
0<=b_n<=a_n. a) if a_n>0 then b_n>0. b) if a_n>infinity then b_n>infinity I don't know where to start. 
Algebra
For the following sequences determine the term indicated: a_1=2, a_n=2(a_n1)^2,a_4 a_n=ln(e^n+2), a_5 b_0=1, b_1=2, b_n+1=2b_nb_0 
Algebra II
1. Which represents the first two terms of the sequence: a_1 = 2 and a_n = 2(a_n1)^2 option a. 8, 128 option b. 16, 1024 option c. 2, 16 option d. 2, 8 2. Which is the seventh term in the sequence: a_n = 1/125 * 5^n1 option … 
DISCRETE MATH
Determine whether the following is a recursive or explicit. Then, find the first four terms of the following sequence. a) a_n = 〖na〗_(n1) where a_0 =5 b) a_n = a_(n1) + 3a_(n2) where a_0 = 1 and a_1 =2 c) a_n = 2^n …