NCERT Class XI Mathematics - Sequences and Series - Solutions
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Question : 51
Total: 106
If the 4th, 10th and 16th terms of a G.P. are x, y and z respectively. Prove that x, y, z are in G.P.
Solution:
Let a be the first term and r be the common ratio, then according to question
a 4 a r 3
a 10 a r 9
a 16 a r 15
Multiplying (i) and (iii), we get
a 2 r 18 ( a r 9 ) 2
⇒y 2
Hence x, y, z are in G.P.
Multiplying (i) and (iii), we get
⇒
Hence x, y, z are in G.P.
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