Question

If n term of an AP is 1/m and m" term is 1/n. Find the sum of its first mn" term.
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Answer 1

Answer:

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Step-by-step explanation:

tn = a + (n - 1)d

1/m = a + (n - 1)d

a = 1/m - nd + d ---- 1)

tm = a + (m - 1)d

1/n = a + (m - 1)d

a = 1/n - md + d ------- 2)

1) = 2)

1/m - nd + d = 1/n - md + d

1/m + 1/n = nd + md

m + n/mn = d(m + n)

d = 1/mn

Sub d = 1/mn in 1)

a = 1/m - 1/m + 1/mn

a = 1/mn

tmn = 1/mn + (mn - 1) × 1/mn

tmn = 0

S = mn/2 (1/mn) = 1/2