Question

the sum of first 20 term in an arithmetic sequence is -520 if 7th term is -5 find u and d?
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Answer 1

Answer:

d= -39 ;a =227

Step-by-step explanation:

a20 = -520

a+19d =-520________(1)

a +6d= -7. ________(2)

solving equation 1 and2

a + 19d =-520

a + 6d =-7

_______________

13d = -517

d = -39

substituting value of d in eq 2

a + 6(-39)= -7

a =-7+234

a = 227