Question

Which of the following are the values of a and b if : (7 + √5) / ( 7 - √5 ) - ( 7 - √5) / ( 7 + √5 ) = a + 7√5 b / 11

a = 2 , b= 1

a = √5 , b = 1

a=0 , b = 1

none of the above

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Answer 1

(c) a = 0, b = 1

(7 + √5) / ( 7 - √5 ) - ( 7 - √5) / ( 7 + √5 ) = a + 7√5 b / 11

=> ((7 + √5)^2 - (7 - √5)^2)/(7 + √5)(7 - √5) = a + 7√5 b/11

=> (7 + √5 + 7 - √5)(7 + √5 - 7 + √5)/(49-5)

=> 28√5/44

=> 7√5/11

Hence the answer.