# week4

What I learned this week was Radicals.

key points:

• An even exponent always gives a positive (or 0) result.
• An Even Root of a Negative Number is Not Real

.

# week 3

I learned absolute value of a real number from week 3.

key note:

the absolute value of x is always either positive or 0, but never negative.

Ex:

# week 2

the thing I learned in this week is Arithmetic sequences／series and Geometric sequences/ series.

### Key notes

• the difference between sequences and series

sequences:5,9,13,17…

series:5+9+13+17…

• importent formula

Arithmetic sequences￼￼

Arithmetic series

geometric sequences

geometric series

Example

• how to solve the Arithmetic series?

ex: Find the sum of the following arithmetic series 1,2,3…..99,100

We have a total of 100 values, so n=100.  first value is 1 and the last is 100. We plug these values into our formula, get:

• how to solve the geometric series?

# my arithmetic sequence

5,10,15,20…

$t_{50}=5+(50-1)5=250$

$s_{50}=\frac{50}{2}(10+(50-1)5)=6375$