已知方程2x²-5x+2=0的两根为x1,x2分别求x1²+x2²和1/x1+1/x2的值
x1+x2=5/2
x1x2=1
x1²+x2²=(x1+x2)²-2x1x2=17/4
1/x1+1/x2=(x1+x2)/(x1x2)=5/2