(x-a)²+(x-b)²≥2(x-a)(x-b)
(a-x)²+(x-b)²≥-2(a-x)(x-b)
a-x+x-b=a-b 为定值
当a-x=x-b时 (a-x)²+(x-b)²有最小值
x=(a+b)/2
(a-x)²+(x-b)²
=(a-(a+b)/2)²+(x-(a+b)/2)²
= (a-b)²/2
(x-a)²+(x-b)²≥2(x-a)(x-b)
(a-x)²+(x-b)²≥-2(a-x)(x-b)
a-x+x-b=a-b 为定值
当a-x=x-b时 (a-x)²+(x-b)²有最小值
x=(a+b)/2
(a-x)²+(x-b)²
=(a-(a+b)/2)²+(x-(a+b)/2)²
= (a-b)²/2