x1x2是方程2X²-3X-8=0的两根
,则X1+X2=3/2 ,
X1X2=-4
,X1²+X2²=(x1+x2)²-2x1x2=9/4+8=41/4
,(X1-2)(X2-2)=x1x2-2(x1+x2)+4=-4-3+4=-3