document.write( "Question 1091788: how many terms of the series -9,-6,-3, ....will be 66? \n" ); document.write( "

Algebra.Com's Answer #706262 by Fombitz(32388) $\"\"$ $\"About$

You can put this solution on YOUR website!
I'm assuming you mean they will sum to 66.
\n" ); document.write( " $\"a%5B1%5D=-9\"$
\n" ); document.write( " $\"d=-6-%28-9%29=-6%2B9=3\"$
\n" ); document.write( "So then,
\n" ); document.write( " $\"S%5Bn%5D=%28n%2F2%29%282a%5B1%5D%2B%28n-1%29d%29\"$
\n" ); document.write( " $\"66=%28n%2F2%29%282%28-9%29%2B%28n-1%29%283%29%29\"$
\n" ); document.write( " $\"n%28-18%2B3n-3%29=132\"$
\n" ); document.write( " $\"n%283n-21%29=132\"$
\n" ); document.write( " $\"n%28n-7%29=44\"$
\n" ); document.write( " $\"n%5E2-7n-44=0\"$
\n" ); document.write( " $\"%28n-11%29%28n%2B4%29=0\"$
\n" ); document.write( "n must be a positive integer so,
\n" ); document.write( " $\"n-11=0\"$
\n" ); document.write( " $\"n=11\"$
\n" ); document.write( " \n" ); document.write( "

\n" );