Math, asked by sshahanaibrahim, 9 months ago

the 8th term of an AP is 120. the sum of the first 8 terms is 540. find the first term and common difference. ​

Answers

Answered by DarkWillow
1

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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