证明:
[∫(a,b)f(x)dx]²
=∫(a,b)f(x)dx∫(a,b)f(y)dy
=∫(a,b)∫(a,b)f(x)f(y)dxdy
≦∫(a,b)∫(a,b)1/2[f²(x)+f²(y)]dxdy
=1/2[∫(a,b)∫(a,b)f²(x)dxdy+∫(a,b)∫(a,b)f²(y)dxdy]
=(b-a)∫(a,b)f²(x)dx.
证毕!
证明:
[∫(a,b)f(x)dx]²
=∫(a,b)f(x)dx∫(a,b)f(y)dy
=∫(a,b)∫(a,b)f(x)f(y)dxdy
≦∫(a,b)∫(a,b)1/2[f²(x)+f²(y)]dxdy
=1/2[∫(a,b)∫(a,b)f²(x)dxdy+∫(a,b)∫(a,b)f²(y)dxdy]
=(b-a)∫(a,b)f²(x)dx.
证毕!