Multiplying or Dividing by a "positive number" will not change the direction of the inequality sign.
Multiplying inequalities by a "positive number".
a = any real number, b = any real number,
c = a "positive" real number not equal to 0
If
a
b
, then
a
*
c
b
*
c
ac
bc
If
a
b
, then
a
*
c
b
*
c
ac
bc
If
a
b
, then
a
*
c
b
*
c
ac
bc
If
a
b
, then
a
*
c
b
*
c
ac
bc
If a = 4, b = 2, c = 2
If
4
2
, then
4
*
2
2
*
2
8
4
If a = 4, b = 6, c = 2
If
4
6
, then
4
*
2
6
*
2
8
12
Dividing inequalities by a "positive number".
a = any real number, b = any real number,
c = a "positive" real number not equal to 0
If
a
b
, then
a
÷
c
b
÷
c
If
a
b
, then
a
÷
c
b
÷
c
If
a
b
, then
a
÷
c
b
÷
c
If
a
b
, then
a
÷
c
b
÷
c
If a = 4, b = 2, c = 2
If
4
2
, then
4
÷
2
2
÷
2
2
1
If a = 4, b = 6, c = 2
If
4
6
, then
4
÷
2
6
÷
2
2
3
Multiplying or Dividing by a "negative number" will change the direction of the inequality sign.
Multiplying inequalities by a "negative number".
a = any real number, b = any real number,
c = a "positive" real number not equal to 0
If
a
b
, then
a
*
(-c)
b
*
(-c)
-ac
-bc
If
a
b
, then
a
*
(-c)
b
*
(-c)
-ac
-bc
If
a
b
, then
a
*
(-c)
b
*
(-c)
-ac
-bc
If
a
b
, then
a
*
(-c)
b
*
(-c)
-ac
-bc
If a = 4, b = 2, c = 2
If
4
2
, then
4
*
(-2)
2
*
(-2)
-8
-4
If a = 4, b = 6, c = 2
If
4
6
, then
4
*
(-2)
6
*
(-2)
-8
-12
Dividing inequalities by a "negative number".
a = any real number, b = any real number,
c = a "positive" real number not equal to 0
If
a
b
, then
a
÷
(-c)
b
÷
(-c)
If
a
b
, then
a
÷
(-c)
b
÷
(-c)
If
a
b
, then
a
÷
(-c)
b
÷
(-c)
If
a
b
, then
a
÷
(-c)
b
÷
(-c)
If a = 4, b = 2, c = 2
If
4
2
, then
4
÷
(-2)
2
÷
(-2)
-2
-1
If a = 4, b = 6, c = 2
If
4
6
, then
4
÷
(-2)
6
÷
(-2)
-2
-3
Multiplying and Dividing an inequality by 0 (zero).
Multiplying inequalities by 0 (zero).
a = any real number, b = any real number
If
a
b
, then
a
*
0
b
*
0
0
0
If a = 4, b = 2
If
4
2
, then
4
*
0
2
*
0
0
0
Dividing inequalities by 0 (zero)- undefined (cannot be done).
a = any real number, b = any real number
If
a
b
, then
a
÷
0
(undefined)
b
÷
0
(undefined)
If a = 4, b = 2
If
4
2
, then
4
÷
0
(undefined)
2
÷
0
(undefined)