Question

if X=9-4√5 find the value of x²+1/x²​

Answer 1

Answer:

Step-by-step explanation:

(9-4√5)² + 1/(9-4√5)²

81+80-72√5 + (9+4√5)²/((9-4√5)(9+4√5))²

161-72√5 + (81+80+72√5)/ (9²-(4√5)²)        using a²-b²=(a-b)(a+b)

161-72√5 + (161 + 72√5)/(81-80)²

161-72√5 + (161 + 72√5)

322