Form 1 Mathematics Chapter 1 Directed Numbers Form 1 Mathematics Chapter 1

Directed numbers on a number line How do we write & say this? + – -6 -2 4 7 7 0 -2 -6 > > > This called “Descending Order” -2 0 4 7 < < < This called “Ascending Order”

Rules to Remember (p.50) ( + ) ( + ) = ( + ) ( – ) ( – ) = ( + ) ( + ) ( + ) = ( + ) ( – ) ( – ) = ( + ) ( + ) ( – ) = ( – ) ( – ) ( + ) = ( – ) 正正得正 負負得正 正負得負 負正得負

Addition and Subtraction (+ A) + (+ B) = A + B (+ A) + (– B) = A – B (– A) + (+ B) = – A + B (– A) + (– B) = – A – B ( + ) ( + ) = ( + ) ( – ) ( – ) = ( + ) ( + ) ( – ) = ( – ) ( – ) ( + ) = ( – ) (+ A) – (+ B) = A – B (+ A) – (– B) = A + B (– A) – (+ B) = – A – B (– A) – (– B) = – A + B

Multiplication and Division (+ A)  (+ B) = A  B (+ A)  (– B) = – (A  B) (– A)  (+ B) = – (A  B) (– A)  (– B) = A  B ( + ) ( + ) = ( + ) ( – ) ( – ) = ( + ) ( + ) ( – ) = ( – ) ( – ) ( + ) = ( – ) (+ A)  (+ B) = A  B (+ A)  (– B) = – (A  B) (– A)  (+ B) = – (A  B) (– A)  (– B) = A  B

Enjoy the world of Mathematics! Good Luck! Enjoy the world of Mathematics! Ronald HUI