Find the sum of the first 9 terms of the sequence. Show all work for full credit.

2, -7, -16, -25, ...

Question

Find the sum of the first 9 terms of the sequence. Show all work for full credit.

2, -7, -16, -25, ...

anonymous · Answer

Are you familiar with Sigma notation?

anonymous · Answer

not at all

texaschic101 · Answer

you could just use the two formulas...one to find the 9th term and one to find the sum

texaschic101 · Answer

you can read about it here.. http://www.regentsprep.org/Regents/math/algtrig/ATP2/ArithSeq.htm or just wait and see what happytales says

anonymous · Answer

OMG

anonymous · Answer

IT JUST BACKSPACED.... OMGGG ARE YOU KIDDING ME

anonymous · Answer

Stupid browser shortcuts -_- let me restart....

anonymous · Answer

Sigma notation is dead useless for solving arithmetic and geometric sequences (and also applications in calculus).  It is typically the most popular method in solving sequences.

The symbol sigma means "to sum".  It looks like this:

$$\sum_{n=1}^{x}$$

The value at the bottom of the symbol indicates the starting value while the top value indicates how many terms to sum up.

For this arithmetic sequence, we can use equation:

$$\sum_{k=0}^{n-1}(a+kd)=\frac{ n }{ 2}(2a+(n-1)d)$$

a= First term
d=Common difference
n=Number of terms

anonymous · Answer

Useful*