A) a²-2ab+b²-3a+3b= (a-b)²-3(a-b)=(a-b)·(a-b-3)=(10/7-(-11/7))·(10/7-(-11/7)-3)=
=(10/7+11/7)·(10/7+11/7-3)=((10+11)/7)·((10+11-21)/7=(21·0)/(7·7)=0/49=0
при a=1 3/7=10/7; b=-1 4/7=-11/7
б) 12,5²+1,2²-(12,5³+1,2³)/13,7=456,25+1,44-(1953,125+1,728)/13,7=315