the first term of GP is 1 the sum of the third and the fifth term is 90 find the common ratio
yubraj111:
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Let first term be a = 1; and common ratio = d;
Then,
ad² + a
= 90
=> + d² - 90 = 0
=> + 10d² - 9d² - 90 = 0
=> (d² - 9) (d² + 10) = 0
=> d² = 9 {Neglecting -10}
=> d = ±3 Hence, the common ratio is ±3.....
Then,
ad² + a
=>
=>
=> (d² - 9) (d² + 10) = 0
=> d² = 9 {Neglecting -10}
=> d = ±3 Hence, the common ratio is ±3.....
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