document.write( "Question 1024168: A GP has the second term as 9 and the fourth term as 81,find the sum of the list as the fourth term \n" ); document.write( "

Algebra.Com's Answer #639731 by Fombitz(32388) $\"\"$ $\"About$

You can put this solution on YOUR website!
$\"a%5B1%5D=a\"$
\n" ); document.write( " $\"a%5B2%5D=a%2Ar=9\"$
\n" ); document.write( " $\"a%5B3%5D=a%2Ar%5E2\"$
\n" ); document.write( " $\"a%5B4%5D=a%2Ar%5E3=81\"$
\n" ); document.write( "So then,
\n" ); document.write( " $\"%28a%2Ar%5E3%29%2F%28a%2Ar%29=81%2F9\"$
\n" ); document.write( " $\"r%5E2=9\"$
\n" ); document.write( " $\"r=3\"$
\n" ); document.write( "and
\n" ); document.write( " $\"a%2A3=9\"$
\n" ); document.write( " $\"a=3\"$
\n" ); document.write( "I think you want the sum of the first 4 terms(?),
\n" ); document.write( "

\n" ); document.write( ".
\n" ); document.write( ".
\n" ); document.write( ".
\n" ); document.write( "It could also be the case that,
\n" ); document.write( " $\"r=-3\"$ and then,
\n" ); document.write( " $\"a%2A%28-3%29=9\"$
\n" ); document.write( " $\"a=-3\"$
\n" ); document.write( "So then,
\n" ); document.write( " $\"S=%28-3%29%281-3%2B9-27%29\"$
\n" ); document.write( " $\"S=60\"$
\n" ); document.write( " \n" ); document.write( "

\n" );