1 , 3 , 6 , 10 , 15 1) What is the nth term of the sequence?

2) Use the nth term to work out the 21st term of the sequence.

First difference,

Second difference,

Third difference,

And so on.

Assuming the pattern holds on, we see that

i-th difference,

Then, nth term is,

Now, the 21st term in the sequence is,

the barter

a

step-by-step explanation:

when a number is between two straight lines it means the absolute value.

to find absolute value you need to know how many numbers is that number away from 0.

when finding absolute value the number will always come out positive

so absolute value of -3 is 3

absolute value of 3/2 is 3/2

absolute value of -2 is 2

absolute value of 3.5 is 3.5

absolute value of -1 is 1

now put these numbers in order:

a)   |-1|, |3/2|, |-2|, |-3|, |3.5|