Question

If x =9-4√5 , find x² +1/x²

Answer 1

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Secondary SchoolMath 5 points


If x=9-4root5 find value of x2+1/x2
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Ask for details FollowReport by Nann 19.10.2014
Answers
shivam2000
shivam2000Ace
x=9-4√5 [Given]
Taking reciprocal.

1/x=1/9-4√5
1/x = [1*(9+4√5)] / [(9-4√5)*(9+4√5)]
1/x=9+4√5/(81-80)
1/x=9+4√5

A.T.Q

x²+1/x²

(9-4√5)² + (9+4√5)²

[9²+(4√5)²-2×9×4√5]+[9²+(4√5)²+2×9×4√5)

[81+80-72√5]+[81+80+72√5]

161-72√5+161+72√5

=322