(x + 1/x)^2 = 9,则x^2 + (1/x)^2 + 2 =9,则袜高x^2 + (1/x)^2 =7;所告唯尺以(x -1/x)^2 = x^2 + (1/山和x)^2 - 2 = 7-2 =5.
你猪啊,连这都不会2
由题意知 (x+1/x)^2=9即:x^2+1+(1/x)^2=9 (1)则(x-1/x)^2=x^2-1+(1/滑纯衡x)^2 (2)将 (1)代入信做裤枝(2)原式=7