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प्रश्न
If the seventh term of an AP is 1/9 and its ninth term is 1/7, find its 63rd term.
उत्तर
Let a be the first term and d be the common difference of the given A.P.
Given:
`a_7=1/9`
`a_9=1/7`
`a_7=a+(7-1)`
`d=1/9`
`=>a+6d=1/9 .........(1)`
`a_9=a+(9-1)d=1/7`
`=>a+8d=1/7......(2)`
Subtracting equation (1) from (2), we get:
2d=2/63
=>d=1/63
Puttingd=1/63 in equation (1), we get:
`a+(6xx1/63)=1/9`
`=>a=1/63`
`∴ a_63=a+(63-1)d=1/63+62(1/63)`
`=63/63=1`
Thus 63rd term of the given A.P. is 1.
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