If the 10th term of an ap is 21 and the sum of the first 10 terms is 120, find its nth term.
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3
Answer:
an = 1+2n
Step-by-step explanation:
a10 =21
a10 = a+9d
a+9d=21 .......................................(1)
S10=10/2[a+a10]
120 =5[a+21] [from eq1]
24=a+21
a=24-21
a=3
Put it into eq1
3+9d=21
d=2
The nth term,
an=a+(n-1)d
an=3+(n-1)2
an=3-2+2d
an=1+2d
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