a²+b²-4a-2b+5=0（a²-4a+4）+(b²-2b+1)=0(a-2)²+(b-1)²=0a=2 b=1√a+√b/√2b-√a-b=(√2+√1)/(√2-√2-1)=(√2+1)/(√2-1)=(√2+1)²/（√2+1）（√2-1）=（2+2√2+1）/（2-1）...