13/15m-3/4m+1/2m при m= 1/2
13/15*1/2-3/4*1/2=13/30-3/8=104/240-90/240=14/240=7/120
13/15*1/2-3/4*1/2+1/2*1/2=13/30-3/8+1/4=74/240=37/120