Question

已知a1,a2属于R,且a1+a2=1,求证a1^2+a2^2大于等于1/2 证明:构造函数f(x)=(x-a1)^2+

Answer 1

结论推广式为：f(x)=(x-a1)^2+……+(x-an)^2 2、证明：f(x) =(x-a1)^2+……+(x-an)^2 =nx^2-2(a1+……+an)x+(a1^2+……an^2) △=4-4n(a1^2+……an^2)=1/n