# Week 2 Geometric Sequence

Determine $S_{10}$ for each geometric series. Give the answer to 3 decimal places. (page 49)

a)0.1+ 0.01+ 0.001+ 0.0001+…

know:$t_{1}$=0.1 ($t_{1}$ means the first one, the first place)

r=0.1( 0.01 divided by 0.1)( each term is multiplied by a constant known as the common ratio) ( to determine the common ratio, divide any  term by the preceding term)

n=10 ( a nautral number and menas the term , for instance, as the question asks to find the 10th term means n= 10)

$S_{10}$

(follow the formula, and use the caluator to caluate the 10th power)

# Week 1- My Arithmetic Sequence

1: my own arithmetic sequence: 20，22，24，26，28，30

first five numbers: 20, 22, 24, 26, 28,30

2: $t_{1}+49d=t_{50}$, d=2

20+49×2=t_{50}=118

3: \$latex t_{1}+(n-1)d=t_{n}

=20+(n-1)2

=20+2n-2

=18+2n

4:(sorry Ms Burton, I don’t know how to type the formula, but I post the process oƒ calculating the sum of the 50 terms)