xC B R,、P RBs Pa b R b A R B pb AC段:Q(x)=RA (0<x<a) pb M(x)=RAx==,x(0≤x≤a) CB段:Q(x)=-RB (a<x<1) M(x)=RB·(l-x) a≤x≤ ) CL7TU8R Pb l R Pa l A = , B = AC段：Q x R Pb l ( ) = A = (0  x  a) M x R x Pb l ( ) = A  = x (0  x  a) CB段：Q x R Pa l ( ) = − B = − (a  x  l) M x R l x Pa l ( ) = B ( − ) = (l − x) (a  x  l) RA RB CL7TU8 P a b l x x A C B