`a) 38 .42`
` = (40-2) . (40+2)`
` = 40^2 - 2^2`
` = 1600 - 4`
` = 1596`
``
`b) 112^2 - 24 . 112 + 12^2`
` = 112^2 - 2 . 112 . 12 + 12^2`
` = (112 - 12)^2`
` = 100^2`
` = 100 00`
``
`c) 298^2 - 297^2`
` = (298 - 297) . (298 + 297)`
` = 1 . 595`
`= 595`
``
`d) 49^2 + 102 . 49 + 51^2`
` = 49^2 + 2 . 49 . 51 + 51^2`
` = (49+51)^2`
` = 100^2`
` = 100 00`