Double negation happens when subtracting a negative number. 

		[image]	[image]	[image]		By double negation[image]
			[image]	[image]		[image]
	[image]					[image]
		[image]	[image]	[image]		By double negation[image]
			[image]	[image]		[image] [image] [image] [image] [image] Why? [image]

Double negation happens when subtracting a negative number. 

This expression involves only addition and subtraction.
So we can do the computations in order from left to right.

	[image]	[image]
[image]	[image]	[image]	[image]Compute[image] , which is[image] .
[image]	[image]		[image]Compute[image] .

Sum of Two Numbers with Unlike Signs (and Different Absolute Values)

To find the sum of two numbers with unlike signs (and different absolute values), subtract their absolute values.

1. The answer is positive if the number with the larger absolute value is positive.

2. The answer is negative if the number with the larger absolute value is negative.

Add two numbers with different signs

We want the sign with the larger absolute value

10 + (-30) =-20

we actually subtract, take the sign with the larger absolute value

-8 + 20 = 12

Add numbers that have the same sign, ignore sign, and take the absolute value.add values and take the common sign

(-13) + (-12) =25

-19 - 13

we actually add the second number. the first number stays the same. subtraction turns to addition.

-19 + (-13) really adding two negative numbers, and keep common sign

-32 is the answer

Dividing by a number is the same as multiplying by its reciprocal.

[image]	[image]		[image]
	[image]		[image]

The fraction [image] is in simplest form.

2. Division involving a whole number and a fraction

Divide. Write your answer in simplest form.

[image]