a^2-2a
x^2+6x
m+m^2+1
3+p^2-p
a^2-2a=a^2-2a+1-1=(a-1)^2-1
x^2+6x=x^2+6x+9-9=(x+3)^2-9
m+m^2+1=m^2+m+0.25-0.25+1=(m+0.5)^2+0.75
3+p^2-p=p^2-p+0.25-0.25+3=(p-0.5)^2+2.75