|R₁|=R₂=R=30 cm=0,3 m
C=(n-1)(1/R₁-1/R₂)=-2(n-1)/|R|=-2(1,5-1)/0,3=-0,5/0,15=-3,33 δ
C=1/f=>f=1/C=1/(-3,33)=-0,3 m=-30 cm
x₂=f/2=-30/2=-15 cm
1/x₂-1/x₁=1/f<=>1/(-15)-1/x₁=1/(-30)<=>-1/15+1/30=1/x₁<=>-1/30=1/x₁=>x₁=-30 cm
β=x₂/x₁=(-15)/(-30)=1/2=0,5
d=|x₁|+|x₂|=15+30=45 cm