上性质2「”6(x)dx=kf(x)d(k为常数 证6f(x)x=im∑4(5,)A →0 =Im∑∫(9Ax1=kim∑f(41)Ax1 →0 i=1 →0 i=1 b kf(x)dx 上页  = b a b a k f (x)d x k f (x)d x (k为常数). 证  b a kf ( x)dx i i n i = k f x = → lim ( ) 1 0   i i n i = k f x = → lim ( ) 1 0   i i n i = k  f x = → lim ( ) 1 0   ( ) .  = b a k f x d x 性质2