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Question
The 4th term of a G.P. is square of its second term, and the first term is –3. Determine its 7thterm.
Solution
Let the first term of the geometric progression, a = –3
And common ratio = r
4th term = ar4 – 1 = ar3 = –3r3
Second term = ar = –3r
Given: 4th term = (second term)2
⇒ –3r3 = (−3r)2
= 9r2
r = –3
7th term = ar7−1 = ar6
= (−3)(−3)6
= (−3)7
= −2187
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