Question

设（a，b）为实数，那么a2+ab+b2-a-2b的最小值是______．

Answer 1

a2+ab+b2-a-2b=a2+（b-1）a+b2-2b

=a2+（b-1）a+

(b-1)2

4

+b2-2b-

(b-1)2

4

=(a+

b-1

2

)2+

3

4

b2-

3

2

b-

1 ...