Răspuns :

1/-x1 + 1/x2 = 2/R; 1/x2 = 2/R + 1/x1; 1/x2 = 2/40 + 1/1000; 1/x2 = 1/20 +1/1000; 1/x1 = 50/1000 + 1/1000; 1/x2 = 51/1000; x2 = 1000/51; x2 = 19,6 cm
/=supra