拉氏变换叠加性的表达式是()a，b为常数AL[af(t)+bf(t)]=aL[f(at)]+bL[f(bt)]BL[af(t)+bf(t)]=aL[af(t)]+bL[bf(t)]CL[af(t)+bf(t)]=aL[f(t)]+bL[f(t)]DL[af(t)+bf(t)]=/aL[f(t)]+/bL[f(t)]