Find d 2

Find d in an A. P. whose 5th term is 18 and 39th term is 120.

Correct result:

d =  3

Solution:

a5=18 a39=120    a5=a1+4 d a39=a1+38 d 18=a1+4 d 120=a1+38 d  a1+4d=18 a1+38d=120  a1=6 d=3



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