Question

已知a2＋4b2－4a＋4b＋5＝0求2a＋b的值

Answer 1

a^2＋4b^2－4a＋4b＋5＝0

(a^2-4a+4)+(4b^2+4b+1)+(5-4-1)＝0

(a-2)^2+(2b+1)^2＝0

解得,

a-2=0,a=2

2b+1=0,b=-1/2

2a+b=2*2+(-1/2)

=4-1/2=3+1/2=3.5