the 8th term of an AP is 120. the sum of the first 8 terms is 540. find the first term and common difference.
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Answer: 15
Step-by-step explanation:
an = a + (n-1) * d #nth term
Sn = n/2 ( 2a + n-1 * d) #sum of n terms
given n=8, an=120, Sn =540
120 = a + 7d --> Eq 1
540 = 8/2 * ( a + an)
= 4* (a + 120)
540/4 = a + 120
135-120 =a
or a = 15
put this in eq 1, to get d = 15
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