а) 910/ 137^2-123^2= 910/(137+123)(1237-123)=910/(260*14)=910/3640=1/4
б)274^2-34^2/960=(274-34)(274+34)/960=240*308/960=73920/960=77
в)53^2-27^2/79^2-51^2=(53-27)(53+27)/(79-51)(79+51)=26*80/28*130=2080/3640=208/364=52/91
г) 14400/324^2-36^2=14400/(324-36)(324+36)=14400/288*360=14400/103680=1440/10368=5/36.