F.1數學

(-30)(+12)(-8)
1. ------------------------
(-18)(-5)

(-360)(-8)
=----------------- (-30)(+12)=(-360) 因為負正得負 , (-18)(-5)=(-90) 因為負負得正
(-90)

2880
=------------ (-360)(-8)=2880 因為負負得正
(-90)

288
=--------- 2880=288 , (-90)=(-9) 因為2880同(-90)大家相約個 0
(-9)

= -32 最後再相除 , 就得到 -32 這答案


2.設他爸今年他爸爸已經x歲

x
5+3 = -----
4

x
8= -----
4

x= 32

今年他爸爸已經32歲

1. (-30)(+12)(-8)
----------------------　　　　＜－－分線
(+18)(-5)

= -(30x12)(-8)
-----------------------
-(18x5)

= (-360)(-8)
-----------------
-90

= +(360x8)
---------------
-90

= 2880
--------
-90

= -32


Note : (+)(+) =(+)
(-) (-) =(+)
(+)( -) =(-)
( -)(+) =(-)


2 . Let y be the age of father now.

1/4y =5+3

1. (-30)(+12)(-8) / (+18)(-5)
= 2880/ -90
= -32
把數乘埋就得

2. Let the age of his father is x
5+3 = x/4
8= x/4
x= 32
三年前5歲, 即今年8歲, 而今年他是他爸的1/4

1. (-30)(+12)(-8) / (+18)(-5) = 2880/-90=-32
2. Let x be the age of son now.
Father age now = x/(1/4) = 4x
x-3=5
x=8
hence, father age now = 4*8=32

2280
______
-90

= -32