Question

if x=√5+2,then find the value of x²+1/x².
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DEAR
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Answer 1

Answer:

18

Step-by-step explanation:

x² = (√5+2)² => 5+4+4√5 => 9+4√5

then

x²+1/x² => 9+4√5 + 1/(9+4√5)

=> [(9+4√5)² + 1] / (9+4√5)

=> (81+80+72√5+1) / (9+4√5)

=> (162+72√5) / (9+4√5)

=> 18(9+4√5) / (9+4√5)

=> 18