28 - ( -32 ) + ( -28 ) - 32 + 5
= 28 + 32 + ( -28 ) - 32 + 5
= ( -28 + 28 ) + ( -32 + 32 ) + 5
= 0 + 0 + 5
= 5
28-(-32)+(-28)-32+5
=[28+(-28)] +[(-32)+32]+5
= 0+0+5=5
mk tính nhanh
28-(-32)+(-28)-32+5
=[28-(-32)+(-28)-32]+5
=0+0+5
=5
28-(-32)+(-28)-32+5
=60+(-28)-32+5
=32-32+5
=0+5
=5