Question

a的2次方+b的2次方+c的2次方-ab-6b-6c+21=0 求a b c的值

Answer 1

a²+b²+c²-ab-6b-6c+21=0

(a²-ab+b²/4)+3(b²/4-2b+4)+(c²-6c+9)

=(a-b/2)²+3(b/2-2)²+(c-3)²=0

b/2-2=0 b=4

c-3=0 c=3

a-b/2=0 a=b/2=4/2=2