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Question
Find the 12th term from the last term of the A.P – 2, – 4, – 6, … – 100
Solution
n = `("l" - "a")/"d" + 1`
= `(-100 - (- 2))/(-2) + 1`
= `(- 100 + 2)/(-2) + 1`
= `(-98)/(-2) + 1`
n = 49 + 1
= 50
12th term from the last = 39th term from the beginning
∴ t39 = a + 38d
= – 2 + 38(– 2)
= – 2 – 76
= – 78
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