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