∵00
∴a/x+b/(2-x)
=[a/x+b/(2-x)]*[x+(2-x)]/2
=[a+b+a(2-x)/x+bx/(2-x)]/2
≥[a+b+2√(ab)]/2
=(√a+√b)²/2
∴最小值=(√a+√b)²/2