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If 2"X"-1/(2"X")=4, Find : 8"X"^3-1/(8"X"^3) - Mathematics

Sum

If `2"x"-1/(2"x")=4`, find : `8"x"^3-1/(8"x"^3)`

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Solution

`2"x"-1/"2x"=4`

`⇒(2"x"-1/"2x")^3=(4)^3`

`⇒(2"x")^3-(1/"2x")^3-3xx2"x"xx1/"2x"(2"x"-1/"2x")=64`

`⇒8"x"^3-1/"8x"^3-3(4)=64`

`⇒8"x"^3-1/"8x"^3-12=64`

`⇒8"x"^3-1/"8x"^3=64+12`

`⇒8"x"^3-1/"8x"^3=76`

Concept: Application of Formulae
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APPEARS IN

Selina Concise Mathematics Class 8 ICSE
Chapter 12 Identities
Exercise 12 (C) | Q 16.2 | Page 155
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