`a, \ 301^2=(300+1)^2=300^2+2.300.1+1`
`=90 \ 000+600+1=90 \ 601`
`b, \ 49^2=(50-1)^2=50^2-2.50.1+1`
`=2500-100+1=2401`
`c, \ 73^2-27^2=(73-27)(73+27)`
`=46.100=4 \ 600`
`d, \ 64.56=(60+4)(60-4)`
`=60^2-4^2=3 \ 600-16=3584`
`e, \ 49^2+2.49.51+51^2`
`=(49+51)^2=100^2=10 \ 00`
`g, \ 97^2-2.97.47+47^2`
`=(97-47)^2=50^2=2 \ 500`