已知X1,X2是函数f(x)=ax^2+bx+1(a,b∈R,a>0)的两个零点,函数f(x)的最小值为-a,记P={x/f(x)

x1+x2=-b/ax1*x2=1/af(x)=a(x^2+b/a*x+b^2/4a^2)-b^2/4a+11-b^2/4a=-ab^2=4a*(1+a)=4a+4a^2(x1+x2)^2=(4a+4a^2)/a^2=4/a+4x1*x2=1/a(x1+x2)^2=4(x1*x2)+4(x1-x2)^2=4x1-x2=2