Asked by adjei
In A.P the difference between the 8th term and 4th term is 20,and the 8th term is one and half times the 4th term.Find the common difference, and the first term.
Answers
Answered by
Reiny
term(8) - term(4) = 20
a + 7d - a - 3d = 20
4d = 20
d = 5
term(8) = (3/2)(term(4))
a+7d = (3/2)(a+3d)
2a + 14d = 3a + 9d
5d = a
a = 25
a=25 ---> first term
d = 5
check:
sequence is:
25, 30, 35, 40, 45, 50, 55, 60, ..
term(8) = 60, term(4) = 20
is 60-40 = 20 ? yes
is 60 = (3/2)(40) ? yes
a + 7d - a - 3d = 20
4d = 20
d = 5
term(8) = (3/2)(term(4))
a+7d = (3/2)(a+3d)
2a + 14d = 3a + 9d
5d = a
a = 25
a=25 ---> first term
d = 5
check:
sequence is:
25, 30, 35, 40, 45, 50, 55, 60, ..
term(8) = 60, term(4) = 20
is 60-40 = 20 ? yes
is 60 = (3/2)(40) ? yes
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