Question

Tính nhanh :

a, 13 . 23 + 22 - 3 . 17 + 28

b, -48 + 48 . (-78) + 48 . (-21)

Answer 1

Bài 1 . Tính nhanh

a) 13 . 23 + 22 - 3 . 17 + 28

= ( 13 + 17 ) . ( 23 - 3 ) . ( 22 + 28 )

= 30 . 20 . 50

= 30000

b) -48 + 48 . ( -78 ) + 48 . ( -21 )

= -48 + [ 48 . ( -78 ) + 48 . ( -21 ]

= -48 + [ 48 . {( -78 ) + ( -21 )} ]

= -48 + [ 48 . -99 ]

= -48 + ( - 4752 )

= -4800

Answer 2

a,13.23+22-3.17+28

=299+22-3.17+28

=321-3.17+28

=318.17+28

=5406+28

=5434

b,-48+48.(-78)+48.(-21)

=[-48+48].(-78)+48.(-21)

=0.(-78)+(-1008)

=0+(-1008)

=(-1008)