document.write( "Question 58694This question is from textbook Algebra 1
\n" ); document.write( ": term 1 2 3 4 ... n
\n" ); document.write( "value 1 3 6 10 ..
\n" ); document.write( "What is the formula for this puzzle????? \n" ); document.write( "
Algebra.Com's Answer #40224 by venugopalramana(3286)\"\" \"About 
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term 1 2 3 4 ... n
\n" ); document.write( "value 1 3 6 10 ..
\n" ); document.write( "What is the formula for this puzzle?????
\n" ); document.write( "t1=1
\n" ); document.write( "t2=3
\n" ); document.write( "t3=6
\n" ); document.write( "t4=10
\n" ); document.write( "------------------------------
\n" ); document.write( "t2-t1=2
\n" ); document.write( "t3-t2=3
\n" ); document.write( "t4-t3=4
\n" ); document.write( "hence
\n" ); document.write( "t5-t4=5
\n" ); document.write( "t6-t5=6
\n" ); document.write( ".......etc
\n" ); document.write( "t(n-1)-t(n-2)=n-1
\n" ); document.write( "tn-t(n-1)=n
\n" ); document.write( "-----------------
\n" ); document.write( "adding all
\n" ); document.write( "tn-t1=2+3+4+......+n
\n" ); document.write( "tn=t1+2+3+4.....n=1+2+3+4......+n=n(n+1)/2
\n" ); document.write( "hence
\n" ); document.write( "tn = n(n+1)/2
\n" ); document.write( "test
\n" ); document.write( "t1=1*2/2=1
\n" ); document.write( "t2=2*3/2=3
\n" ); document.write( "t3=3*4/2=6
\n" ); document.write( "t4=4*5/2=10
\n" ); document.write( "ok.. \n" ); document.write( "
\n" );