Представь в виде дроби
(t-t/u)(t+t/u)=t²-t²/u²=(t²u²-t²)/u²=t²(u²-1)/u² (10-m/v)(10+m/v)=10²-m²/v²=(100v²-m²)/v² (10-m/v):(10+m/v)=(10v-m)/v : (10v+m)/v= =(10v-m)/v . v/(10v+m)=(10v-m)/(10v+m)