已知实数abc满足a=6-b,c^2=ab-9,求abc

题目

已知实数abc满足a=6-b,c^2=ab-9,求abc

答案

c^2=ab-9=(6-b)*b-9>=0
b^2-6b+9<=0
(b-3)^2<=0
因为(b-3)^2>=0
so(b-3)^2=0
sob=3
a=6-3=3
c=0
所以a=3
b=3
c=0
abc=0