if 6 times the sixth term of an arithmetic progression is equal to 9 times the 9th term. Find the 15th term.
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6t6=9t9
To find: t15
tn=a+(n-1)d
6* (a+(6-1)d)= 9*(a+(9-1)d)
6*(a+5d)= 9*(a+8d)
6a+30d=9a+72d
9a+72d-6a-30d=0
3a+42d=0
÷3
a+14d=0
a+(15-1)d=0
•°• t15= 0
To find: t15
tn=a+(n-1)d
6* (a+(6-1)d)= 9*(a+(9-1)d)
6*(a+5d)= 9*(a+8d)
6a+30d=9a+72d
9a+72d-6a-30d=0
3a+42d=0
÷3
a+14d=0
a+(15-1)d=0
•°• t15= 0
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