[Zentriol]

x^4+2x^3+2x^2+x+2
=x^2(x+1)^2+x(x+1)+2
=(x(x+1)+1/2)^2 + 7/4
=(x^2+x+1/4) +1/4)^2 +7/4
=((x+1/2)^2 +1/4 )^2 +7/4
=ค่าต่ำสุดก็ต่อเมื่อx+1/2 =0
\therefore ค่าต่ำสุด= (1/4)^2 + 7/4 = 29/16