中一數學點做好?

(-7.2)-(+2.3)+(-5)
=(-9.5)+(-5)
= -14.5

Because Negative - Positive = Negative ( -7.2 - +2.3)
Because Negative + Negative = Negative ( -9.5 + -5)

你數學唔得ar...

2007-09-21 23:49:13 補充：
keslieslyt...正正得正,負負得正,正負得負,負正得負,係乘法arPositive+Positive=PositiveNegative+Negative=NegativePostive+Negative=Positive - PositiveNegative+Positive=Positive - Positive

2007-09-21 23:49:29 補充：
Positive - Positive=Positive/NegativeNegative - Negative= Negative+PositivePositive- Negative= Positive+PositiveNegative - Positive= Negative

(-7.2)-(+2.3)+(- 5)
=(-7.2)-2.3-5
=-9.5-5
=-14.5

very easy!

(-7.2) - (+2.3) + (-5)
=(-7.2) - 2.3 - 5
=-(7.2 + 2.3 + 5)
=-14.5

順便教下你:

- (+2.3) 這樣是一組，而最前面的(-7.2)其實是+ (-7.2)。
如果個組的2個符號一樣，就是加；反之，就是減。

2007-09-21 23:55:10 補充：
咁快教到這裏了嗎?

(-7.2)-(+2.3)+(-5)
=(-9.5)+(-5)
= -14.5

U can also use the calculator^^

我都係岩岩升中一@@
(-7.2)-(+2.3)+(-5)
=-7.2-2.3-5
=-12.5

(-7.2)-(+2.3)+(-5)
7.2後面係唔係有2個符號(-+)負正得負
所以就變成-7.2-2.3
而2.3後面又有個(+-)正負得負
所以成條係
-7.2-2.3-5

2007-09-21 23:45:46 補充：
答案係-14.5先岩- -我kai在...計錯數= =

(-7.2)-(+2.3)+(-5)
= -7.2 - 2.3 - 5
= -9.5 - 5
= -14.5

用計算機囉..

答案:: -14.5

記得..
正正得正

負負得正

正負得負

負正得負


就會易做好多‥

++得+
- - 得+
+ -得 -
- + 得-

(-7.2)-(+2.3)+(-5)

= -7.2 - 2.3 - 5
= -14.5

(-7.2)-(+2.3)+(-5)
= -7.2 - 2.3 - 5
= -9.5 - 5
= -14.5