∵f(2x+1)=8x+74x2+4x+2，∴f（2x+1）=4(2x+1)+3(2x+1)2+1即f（x）=4x+3x2+1令f'（x）=-2(x+2)(2x-1)(x2+1)2=0解得x=-2或12当x∈（-∞，-2）时f'（x）=-2(x+2)(2x-1)(x2+1)2＜0当x∈（-2，12）时f'（x）=-2(x+2)(2x-...