(0,8^-2+ 0,6^-2)^-1
0,8^(-2)=(10/8)^2=100/64 0,6^(-2)=(10/6)^2=100/36 (100/64)+(100/36)=100*(36+64)/(64*36)=100*100/(64*36) (100*100/(64*36))^(-1)=(64*36)/10000=0,2304