已知函数f(x)=x^2lga+2x+4lga最大值为3,求实数a的值

f(x) = x^2lga + 2x + 4lga的最大值为3,因此,lga < 0. 0 < a < 1.f(x)的对称轴位于 x = -1/lga,3 = f(-1/lga) = (-1/lga)^2(lga) + 2(-1/lga) + 4lga = 1/lga -2/lga + 4lga = 4lga -1/lga,4(lga)^2 - 3lga - 1 = [4...