Find : "A"^3+1/"A"^3, If "A" +1/"A"=5. - Mathematics

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Sum

Find : `"a"^3+1/"a"^3`, if `"a"  +1/"a"=5`.

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Solution

`"a"  +1/"a"=5`

`⇒("a"+1/"a")^3=(5)^3`

`⇒"a"^3+1/"a"^3+3"a"xx1/"a"("a"+1/"a")=125`

`⇒"a"^3+1/"a"^3+3(5)=125` ........`["a"+1/"a"=5]`

`⇒"a"^3+1/"a"^3+15=125`

`⇒"a"^3+1/"a"^3=125-15`

`⇒"a"^3+1/"a"^3=110`

Concept: Application of Formulae
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APPEARS IN

Selina Concise Mathematics Class 8 ICSE
Chapter 12 Identities
Exercise 12 (C) | Q 14 | Page 155
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