Aug. 25, 2009

Warm up:

1. (x-y)/(r-s) when x=9, y=-3, r=23, s=-1
Step 1: (9--3)/(23--1)
Step 2: (12)/(24)
Step 3: 1/2 or .5


Fool proof way to add negative numbers:
+2 +3
-2 +3
+2 -3
-2 -3

Four ways to write 2 and 3.
Two words for making this simple:
1. SAME = +2 +3 and -2 -3 are the same sign.
IF SAME -> ADD -> KEEP

Ex: +2 +3
Add = 5
Keep = +
Answer = +5

Ex: -2 -3
Add = 5
Keep = -
Answer = -5

2. DIFFERENT = -2 +3 and +2 -3 are different signs.
IF DIFFERENT-> SUBTRACT-> LARGER

Ex: -2 +3
Subtract= 3-2
Keep = + (3 is bigger than 2)
Answer = +1

Ex: +2 -3
Subtract= 3-2
Keep = - (3 is bigger than 2)
Answer = -1