2x^2+3x-1=0
x1+x2=-3/2 x1*x2=-1/2
x1^2+x2^2=(x1+x2)^2-2x1*x2=9/4-2*(-1/2)=13/4
1/x1 +1/x2=(x1+x2)/x1*x2=-3/2 *(-2)=3