解
x1,x2是方程两根
则有韦达定理有
x1+x2=-3/4
x1x2=-5/4
∴
(1)1/x1+1/x2
=(x1+x2)/(x1x2)
=(-3/4)×(-4/5)
=3/5
(2)x1²-x1x2+x2²
=(x1+x2)²-3x1x2
=(-3/4)²+3×(5/4)
=9/16+15/4
=69/16