1
ab+a+b=3
a(b+1)+b+1=4
(a+1)(b+1)=4
同理(b+1)(c+1)=4,(a+1)(c+1)=4
三个式子相乘得((a+1)(b+1)(c+1))的平方=64
(a+1)(b+1)(c+1)=8
2
a^2+b^2+c^2-ab-ac-bc=0
2a^2+2b^2+2c^2-2ab-2ac-2bc=0
a^2+b^2-2ab+b^2+c^2-2bc+a^2+c^2-2ac=0
(a-b)^2+(b-c)^2+(a-c)^2=0
a-b=b-c=a-c=0
∴a=b=c,等边
3
a^2+c^2=m^4-2m^2+1+4m^2=m^4+2m^2+1=(m^2 +1)^2=b^2
直角三角形