-2x²+8x+2
=-2x²+8x-8+8+2
=-2(x²-2x+1)+10
=-2(x-1)²+10
∵ x不论取什么值,-2(x-1)²+10≥10
∴对任意实数x,代数式-2x2+8x+2的总值不大于10