document.write( "Question 259658: three numbers are in AP and their sum is 21. if 1,5,15 are added to them respectively,they form a GP.The numbers are.
\n" ); document.write( "please tell me the solution and method of solving this type of questions using this formula for Ap:(a-d),a, (a+d) and for GP:a/r,a,ar
\n" ); document.write( "the option for the above question is :A)5,7,9 B)9,7,5 C) none of these\r
\n" ); document.write( "\n" ); document.write( "the above is question of AP and GP.
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Algebra.Com's Answer #191104 by Fombitz(32388)\"\" \"About 
You can put this solution on YOUR website!
Let A be your starting number, d be the difference for the arithmetic progression.
\n" ); document.write( "\"A%2B%28A%2Bd%29%2B%28A%2Bd%2Bd%29=21\"
\n" ); document.write( "\"3A%2B3d=21\"
\n" ); document.write( "\"A%2Bd=7\"
\n" ); document.write( "Then from the geometric progression information,
\n" ); document.write( "First:\"A%2B1\"
\n" ); document.write( "Second:\"A%2Bd%2B5\"
\n" ); document.write( "Third:\"A%2Bd%2Bd%2B15=A%2B2d%2B15\"
\n" ); document.write( "Since they are in geometric progression, each successive pair equals the common ratio.
\n" ); document.write( "\"%28A%2Bd%2B5%29%2F%28A%2B1%29=%28A%2B2d%2B15%29%2F%28A%2Bd%2B5%29\"
\n" ); document.write( "From eq. 1, you know,
\n" ); document.write( "\"A%2Bd=7\"
\n" ); document.write( "Substitute,
\n" ); document.write( "\"%28A%2Bd%2B5%29%2F%28A%2B1%29=%28A%2B2d%2B15%29%2F%28A%2Bd%2B5%29\"
\n" ); document.write( "\"%287%2B5%29%2F%28A%2B1%29=%287%2Bd%2B15%29%2F%287%2B5%29\"
\n" ); document.write( "\"12%2F%28A%2B1%29=%2822%2Bd%29%2F12\"
\n" ); document.write( "\"%28A%2B1%29%2822%2Bd%29=144\"
\n" ); document.write( "Again using eq. 1,
\n" ); document.write( "\"A%2Bd=7\"
\n" ); document.write( "\"d=7-A\"
\n" ); document.write( "\"%28A%2B1%29%2822%2Bd%29=144\"
\n" ); document.write( "\"%28A%2B1%29%2822%2B7-A%29=144\"
\n" ); document.write( "\"%28A%2B1%29%2829-A%29=144\"
\n" ); document.write( "\"29A-A%5E2%2B29-A=144\"
\n" ); document.write( "\"-A%5E2%2B28A%2B29=144\"
\n" ); document.write( "\"-A%5E2%2B28A-115=0\"
\n" ); document.write( "\"A%5E2-28A%2B115=0\"
\n" ); document.write( "You can factor,
\n" ); document.write( "\"%28A-23%29%28A-5%29=0\"
\n" ); document.write( "Two solutions:
\n" ); document.write( "\"A-23=0\"
\n" ); document.write( "\"A=23\"
\n" ); document.write( "\"d=7-A\"
\n" ); document.write( "\"d=7-23=-16\"
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\n" ); document.write( "\"A-5=0\"
\n" ); document.write( "\"A=5\"
\n" ); document.write( "\"d=7-A\"
\n" ); document.write( "\"d=7-5=2\"
\n" ); document.write( ".
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\n" ); document.write( "A) (5,7,9) is one solution.
\n" ); document.write( "But (23, 7, -9) is also a solution.
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