原式=26x28x1/26x27+26x28x1/27x28
=27x28+26x28x1/27x27+26x28x1/27
=28x(27+26+26/27)
=28x(50+3+26/27)
=28x50+28x3+27x26/27+26/27
=1400+84+26+26/27
=1510又26/27
解:26×28×(1/26×27+1/27×28)=26×28×(1/(26x27))+26×28×(1/(27x28))=28/27+26/27 =(28+26)/27 =54/27 =2