Sequences.. ?

**cu4mail** · November 8th 2007, 03:21 AM

Dear All,

I need help to solve these questions on sequences..

Q1. Write the first rour terms of the following sequences
If
i) $a_n = (-1)^n (2n-3)$

ii) $a_n - a_{n-1} = n + 2, a_1 = 2$

Q2. Which term of the arithmetic sequence -2, 4, 10, .... is 148?

Q3. Find the 11th term of the sequence 1+i, 2, 4/1+i, .... where i^2 = -1

Answers with some description will help me to understand the methodology.

Thanks in Advance

**kalagota** · November 8th 2007, 04:47 AM

Originally Posted by cu4mail

Dear All,

I need help to solve these questions on sequences..

Q1. Write the first rour terms of the following sequences
If
i) $a_n = (-1)^n (2n-3)$

ii) $a_n - a_{n-1} = n + 2, a_1 = 2$

all you have to do is to replace n by 1, 2, 3, and 4..

Originally Posted by cu4mail

Q2. Which term of the arithmetic sequence -2, 4, 10, .... is 148?

note that $a_n = a_1 + (n-1)d$ , where d is the common difference.. you see in the sequence that $a_1 = -2$ and d=6. so,
$a_n = 146 = -2 + (n-1)6$ . solve for n.

Originally Posted by cu4mail

Q3. Find the 11th term of the sequence 1+i, 2, 4/1+i, .... where i^2 = -1

Answers with some description will help me to understand the methodology.

Thanks in Advance

note that $\frac{2}{1+i} = \frac{\frac{4}{1+1}}{2}$ so that the sequence is Geometric..
so use the formula $a_n = a_1 r^{n-1}$ , where r is the common ratio..

**Plato** · November 8th 2007, 06:02 AM

Originally Posted by kalagota

note that $\frac{2}{1+i} = \frac{\frac{4}{1+1}}{2}$ so that the sequence is Geometric..
so use the formula $a_n = a_1 r^{n-1}$ , where r is the common ratio..

Actually $\frac{2}{1+i} = { 1-i }$

Thread: Sequences.. ?

LinkBack

Thread Tools

Display

Sequences.. ?

Similar Math Help Forum Discussions

Convergence in sequences of sequences

Sequences and the sequences' arithmetics

Monotone sequences and Cauchy sequences

Sequences Q3

The formulas for Algebraic Sequences and Geometric Sequences

Search Tags