x^3-y^3= (x-y)(x^2+2xy+y^2)=10xy+15
DIEN DAU >
dap so la1348
chuan luon . hihi
240 : 4 = 60 cm
60 nhân 60 bằng 3600 cm2
=900+1000+2000
=1900+2000
=3900