document.write( "Question 1055154: The sum of the second and the third terms of a geometric progression is 6,the sum of the third and the fourth term is -12.find;
\n" ); document.write( " (a) first term
\n" ); document.write( " (b) common ratio
\n" ); document.write( " (c) sum of the first 20 terms \n" ); document.write( "

Algebra.Com's Answer #670473 by Fombitz(32388) $\"\"$ $\"About$

You can put this solution on YOUR website!
$\"a%5B1%5D=a\"$
\n" ); document.write( " $\"a%5B2%5D=a%2Ar\"$
\n" ); document.write( " $\"a%5B3%5D=a%2Ar%5E2\"$
\n" ); document.write( " $\"a%5B4%5D=a%2Ar%5E3\"$
\n" ); document.write( "So then,
\n" ); document.write( " $\"a%5B1%5D%2Ba%5B3%5D=a%2Bar%5E2=6\"$
\n" ); document.write( " $\"a%281%2Br%5E2%29=6\"$
\n" ); document.write( "and
\n" ); document.write( " $\"a%5B3%5D%2Ba%5B4%5D=a%5Er%5E2%2Bar%5E3=-12\"$
\n" ); document.write( " $\"ar%5E2%281%2Br%29=-12\"$
\n" ); document.write( "I graphed these two equations substituting (x,y) for (a,r) and found an intersection point.
\n" ); document.write( " $\"a=0.535\"$
\n" ); document.write( " $\"r=-3.196\"$
\n" ); document.write( "So then,
\n" ); document.write( " $\"S=a%28%281-r%5EN%29%2F%281-r%29%29\"$
\n" ); document.write( " $\"S=0.535%28%281-%28-3.196%29%5E20%29%2F%281-%28-3.196%29%29%29\"$
\n" ); document.write( " $\"S=-1574882205\"$
\n" ); document.write( " \n" ); document.write( "

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