设f(x)=ax+b,则
∫(0,1)f(x)dx=∫(0,1)(ax+b)dx=a/2+b=1,
b=1-a/2.
∫(0,1)[f(x)]^2dx=∫(0,1)[a^2x^2+2abx+b^2]dx
=a^2/3+ab+b^2
=a^2/3+a(1-a/2)+(1-a/2)^2
a^2/12+1≥1.
设f(x)=ax+b,则
∫(0,1)f(x)dx=∫(0,1)(ax+b)dx=a/2+b=1,
b=1-a/2.
∫(0,1)[f(x)]^2dx=∫(0,1)[a^2x^2+2abx+b^2]dx
=a^2/3+ab+b^2
=a^2/3+a(1-a/2)+(1-a/2)^2
a^2/12+1≥1.