Question

二次根式乘法若x+1/x=3 求x-1/x 等于多少,

Answer 1

(x+1/x)^2=9

展开

x^2+1/x^2=7

x^2+1/x^2-2=5

故

(x-1/x)^2=5

x-1/x=正负根号五