(42- 69 +17)-(42+17)
= 42-69 +17- 42-17
=-69
đap số -69
= 42-69+17-42-17
= -27+17-42-17
= -10-42-17
= -52-17
= -69
= 42 - 69 + 17 - 42 + 17
= ( 42 - 42 ) - ( 17 - 17 ) - 69
= 0 - 0 - 69
= ( - 69 )
(42-69+17)-(42+17)
=42-69+17-42-17
=(42-42)+(17-17)-69
=0+0-69
=-69