377.b/(a-b)*(1/a-1/b)=b/(a-b)*((b-a)/ab)=b*(b-a)/(a-b)*ab= -b/ab=-1/a 378. b/(2a-b)*(1/a-2/b)=b/(2a-b)*((b-2a) /ab)=-b/ab=- 1/a ......379.a/(a-3b)*(3/a-1/b)=a/(a-3b)*((3b-a)/ab)=-a/ab=-1/b ...........380. a/(5a-7b)*(7/a-5/b)=a/(5a-7b)*((7b-5a)/ab)=-a/ab=-1/b ....381. (u/v +4v/u-4)* uv/(2v-u)= (u^2+4v^2-4uv)/uv)*uv/(2v-u)=(u-2v)^2/(2v-u)=u-2v ...............................................................................382.(4u/v+9v/u+12)* uv/(3v+2u)=( 4u^2+9v^2+12uv)/uv * uv/(3v+2u)=(2u+3v)^2/(3v+2u)=2u+3v ......383.(36u/v+v/u-12)* uv/(v-6u)=(36u^2+v^2-12uv)/uv * uv/(v-6u)=(6u-v)^2/(v-6u)=6u-v....................384.(81u/v+4v/u+36)* uv/(2v+9u)=(81u^2+4v^2+36uv)/uv *uv/(2v+9u)=(9u+2v)^2/(2v+9u)=9u+2v