原式=-(99+(98/99))*198=-(99+(98/99))*99*2=-(99^2+98)*2=-((100-1)^2+98)*2=-((10000-200+1)+98)*2=-9899*2=-19798
负99又99分之98乘198=-(100-99分之1)×198=-100×198+99分之1×198=-19800+2=-19798
= -(100 -1/99) ×198 = -100 ×198 +1/99 ×198 = -19800 +2= -19798