`a)33.55+33.67+45.33+67.67`
`=(33.55+45.33)+(33.67+67.67)`
`=33.(55+45)+67.(33+67)`
`=33.100+67.100`
`=100.(33+67)`
`=100.100`
`=10000`
`b)25^2+35^2-90+70.25`
`=(25^2+70.25+35^2)-90`
`=(25^2+2.25.35+35^2)-90`
`=(25+35)^2-90`
`=60^2-90`
`=3600-90`
`=3510`
mk gửi nha~
$#chúc tus học tốt!!$