x1,x2 - pierwiastki równania kwadratowego ax²+bx+c=0 ,a≠0
1/x1+1/x2=(x1+x2)/x1x2=(-b/a):(c/a)=-b/a·a/c=-b/c
A. 3x²-x-1=0 , b=-1 , c=-1
-b/c=1/(-1)=-1
B. -2x²-8x-3=0 , b=-8 , c=-3
-b/c=8/(-3)=-8/3
C. 4x²+20x-6=0 , b=20 , c=-6
-b/c=-20/(-6)=20/6=10/3=3 1/3
