Mathematics
If 5th, 8th and 11th terms of a G.P. are x, y and z respectively, then which one of the following is correct?
y2 = x2z2
y2 = x2 + z2
y2 = xz
xyz = 1
G.P.
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Answer
Let first term of G.P. be a and common ratio be r.
Given,
5th term = x
x = ar5 - 1
x = ar4
8th term = y
y = ar8 - 1
y = ar7
11th term = z
z = ar11 - 1
z = ar10
Substituting value of y in L.H.S. of y2 = xz
⇒ y2
⇒ (ar7)2
⇒ (a2r14)
Substituting value of x and z in R.H.S. of y2 = xz
⇒ xz
⇒ ar4 × ar10
⇒ a2r14.
Since, R.H.S. = L.H.S.
Hence proved, that y2 = xz.
Hence, option 3 is the correct option.
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