CBSEi Class 10 Sequences (AP and GP) CORE
CBSEi Class 10 Sequences (AP and GP) CORE
CBSEi Class 10 Sequences (AP and GP) CORE
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– =<br />
= =<br />
=<br />
Thus, it is not an <strong>AP</strong> (Why?) [Note that denominators 7, 9, 11, 13,…. are in<br />
<strong>AP</strong>, check!!]<br />
(v) 1, 1.7, 2.4, 3.1,….<br />
We have,<br />
1.7 – 1 = 0.7<br />
2.4 – 1.7 = 0.7<br />
3.1 – 2.4 = 0.7<br />
So, it is an <strong>AP</strong> with common difference (d) = 0.7<br />
(vi) 1 2, 5 2, 7 2, 73,….<br />
1 2, = 1, 5 2 = 25, 7 2 = 49, 73 =73.<br />
Further,<br />
25 1 = 24<br />
49 25 = 24<br />
73 – 49 = 24<br />
So, 1 2 , 5 2 , 7 2 , 73,…. is an <strong>AP</strong> with common difference (d) = 24<br />
Example 5: Find the value of k for which k+2, 4k 6 <strong>and</strong> 3k 2 form three consecutive<br />
terms of an <strong>AP</strong>.<br />
Solution: a = k+2, a+d = 4k 6, a+2d = 3k 2, where d is the common difference.<br />
If k+2, 4k 6, 3k 2 are in <strong>AP</strong>, then<br />
d = (a+d) a = (4k 6) (k+2) = 3k 8 (1)<br />
Also, d = (a+2d) (a+d) = (3k 2) – (4k 6) = 4 k (2)<br />
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