maths Q

x^0.5+x^-0.5=3
sqrt(x) + 1/(sqrt(x)) = 3
之後2邊都2次方
(sqrt(x) + 1/(sqrt(x)))^2 = 3^2
x + 2 sqrt(x)/sqrt(x) + 1/x = 9
x + 2 + 1/x = 9
x + 1/x = 7
x+(1 over x )= 7

2008-05-23 21:23:23 補充：
What is the value of X?
2邊 * x
x ^ 2 + 1 = 7x
x^2 - 7x + 1 = 0
x^ 2 - 7x = -1
2邊加 (7/2)^2
x^ 2 - 7x + (7/2)^2 = -1 +49/4
(x - 7/2)^2 = 45/4
x - 7/2 = 3 sqrt(5)/2 OR -3 sqrt(5)/2
x =(7+ 3 sqrt(5))/2 OR (7-3sqrt(5))/2