Question
If a = `(sqrt(5) + 1)/(sqrt(5) - 1)` and b= `(sqrt(5) - 1)/(sqrt(5) +1)` , the value of `((a^2 + ab + b^2)/(a^2 - ab + b^2))`
is
Answer: Option B
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a = `(sqrt(5) + 1)/(sqrt(5) - 1)` x `(sqrt(5) + 1)/(sqrt(5) +1)` = `((sqrt(5) + 1)^2)/((5 - 1))`
= `(5 + 1 + 2sqrt(5))/(4)` = `((3 + sqrt(5))/(2))`
b= `(sqrt(5) - 1)/(sqrt(5) +1)` x `(sqrt(5) - 1)/(sqrt(5) -1)` = `((sqrt(5) - 1)^2)/((5 - 1))` = `(5 + 1 - 2sqrt(5))/(4)`
= `((3 - sqrt(5))/(2))`
`:.` `a^2 + b^2` = `((3 + sqrt(5))^2)/(4)` + `((3 - sqrt(5))^2)/(4)` = `((3 + sqrt(5))^2 +(3 - sqrt(5))^2)/(4)`
`(2(9 + 5))/(4)` = 7.
Also, ab = `((3 + sqrt(5) (3 - sqrt(5))/(2)` = ` (9 - 5)/4` = 1
`:.` ` (a^2 + ab + b^2)/(a^2 - ab + b^2)` = `((a^2 b^2) + ab)/((a^2 + b^2) - ab)` = `(7 + 1)/(7 - 1)` = `8/6` = `4/3`
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