12. 5th,8th, and 11th terms of a G.P. arep, q and s respectively, prove that q²? = ps.
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Step-by-step explanation:
Show that q2 = ps. Let a be the first term and r be the common ratio of the G.P. Thus, the given result is proved.
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Given that:
5th term = P
8th term = q
11th term = s
To prove that: q^2 = ps
By using the above information, we can write the equation as:
a5 = ar5-1 = ar4 = p ….(1)
a8 = ar8-1 = ar7 = q ….(2)
a11 = ar11-1 = ar10 =s …(3)
Divide the equation (2) by (1), we get
r^3 = q/p …(4)
Divide the equation (3) by (2), we get
r^3 = s/q …(5)
Now, equate the equation (4) and (5), we get
q/p = s/q
It becomes, q^2 = ps
Hence proved.
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