(a-b)²
=a²+b²-2ab
=(a+b)²-4ab a+b=8 ab=15 代入
=64-60
=4
则a-b= ± 2
因为原题中a>b 则a-b>0
a-b= 2
x+1/x=8 x* 1/x=1
(x-1/x)²
=(x+1/x)²- 4*x* 1/x
=8-4=4
x-1/x =±2
(a-b)²
=a²+b²-2ab
=(a+b)²-4ab a+b=8 ab=15 代入
=64-60
=4
则a-b= ± 2
因为原题中a>b 则a-b>0
a-b= 2
x+1/x=8 x* 1/x=1
(x-1/x)²
=(x+1/x)²- 4*x* 1/x
=8-4=4
x-1/x =±2