xy
yx
(xy)1n−2
(yx)1n−2
Correct answer is D
Sum of nth term of a G.P = Sn = arn−1r−1
sum of the first two terms = ar2−1r−1
x = a(r + 1)
sum of the last two terms = Sn - Sn - 2
= arn−1r−1 - (arn−1)r−1
= a(rn−1−rn−2+1)r−1 (r2 - 1)
∴ arn−2(r+1)(r−1)1= arn - 2(r + 1) = y
= a(r + 1)r^n - 2
y = xrn - 2
= yrn - 2
yx = r = (yx)1n−2
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