a²+3b²-3a-3b=-3
a²-3a+3b²-3b+3=0
a²-3a+(3/2)²-(3/2)²+3(b²-b)+3=0
a²-3a+(3/2)²-(3/2)²+3(b²-b+(1/2)²-(1/2)²)+3=0
(a-3/2)² -9/4+3(b-1/2)²-3/4+3=0
(a-3/2)² +3(b-1/2)²=0
(a-3/2)=0 (b-1/2)=0
则有a=3/2 b=1/2