Question

if x is equal to 9 + 4 root 5 find X square + 1 by x square

Answer 1

Answer:

x²+1/x²  = 322

Step-by-step explanation:

x = 9+4√5

1/x = 1/(9+4√5)   * (9-4√5)/(9-4√5)

    = (9-4√5)/(9²- [4√5]²)

    = (9-4√5)/(81-80) = 9-4√5

x² = (9+4√5)² = 9²+(4√5)²+9*4√5*2

                      = 81+80+72√5

                      = 161+72√5

1/x² = (9-4√5)²

      = 9² +(4√5)²-2*9*4√5

      = 81+80-72√5

      = 161-72√5

x²+1/x² = 161+72√5 + 161-72√5

           = 322

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Answer 2

Step-by-step explanation:

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