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B
±√27
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C
±√23
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D
±√22
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Solution
The correct option is B±√29 a2−5a−1=0 =>a2−1=5a =>a−1a=5 Squaring both sides, we get =>a2+1a2−2a×1a=25 =>a2+1a2=25+2 =>a2+1a2=27 Now, (a+1a)2=a2+1a2+2a×1a =a2+1a2+2 =27+2 =29 Thus, a+1a=±√29