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Determine whether the expansion of (x2-2x)18 will contain a term containing x10? - Mathematics

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प्रश्न

Determine whether the expansion of `(x^2 - 2/x)^18` will contain a term containing x10?

योग
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उत्तर

Let Tr+1 contain x10.

Then Tr+1 = `""^18"C"_r  (x^2)^(18 - r)  (-2^r)/x`

= `""^18"C"_r  x^(36 - 2r)  (-1)^r  * 2^r  x^(-r)`

= `(-1)^r  2^r  ""^18"C"_r  x^(36 - 3r)`

Thus, 36 – 3r = 10

i.e., r = `36/3`

Since r is a fraction, the given expansion cannot have a term containing x10.

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अध्याय 8: Binomial Theorem - Solved Examples [पृष्ठ १३३]

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एनसीईआरटी एक्झांप्लर Mathematics [English] Class 11
अध्याय 8 Binomial Theorem
Solved Examples | Q 6 | पृष्ठ १३३

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