If R − 1 R = 4 ; Find: R 2 + 1 R 2 - Mathematics

If `"r" - (1)/"r" = 4`; find: `"r"^2 + (1)/"r"^2`

Sum

`("r" - 1/"r")^2`

= `"r"^2 + (1)/"r"^2 - 2`

⇒ (4⁾² = `"r"^2 + (1)/"r"^2 - 2`

⇒ `"r"^2 + (1)/"r"^2`
= 16 + 2
= 18.

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