Linear Inequations
Inequation:
The mathematical statement in which the quantity on one side is not equal to the quantity on the
other side is called an inequation.
Representation of linear inequality in one variable:
Let a, b and c be real numbers.
ax + b > c                   ax + b is greater than c
ax + b < c                   ax + b is less than c
ax + b ≥ c                   ax + b is greater than or equal to c
ax + b ≤ c                   ax + b is less than or equal to c
The signs '>'; '<'; '≤'; '≥' are called signs of inequality.
Solving a Linear Inequality Algebraically:
             When a positive term is moved from one side of
Rule 1       an inequality to another, the sign of the term         2x + 3 > 7 = 2x > 7 – 3
             becomes negative
             When a negative term is moved from one side of
Rule 2       an inequality to another, the sign of the term         2x – 3 > 7 = 2x > 7 + 3
             becomes positive
                                                                                               1
              When each term of an inequality is multiplied or
                                                                      x < y = px <py
Rule 3        divided by the same positive number (p), the sign
                                                                      x < y = x/p < y/p
              of the inequality remains unchanged
              When each term of an inequality is multiplied or
                                                                      x < y = px >py
Rule 4        divided by the same negative number (p), the
                                                                      x < y = x/p > y/p
              sign of the inequality reverses
              If the sign of each term on both the sides of an
Rule 5        inequality is changed, the sign of inequality gets      –x>5=x<–5
              reversed
              If both the sides of an inequality are either
Rule 6        positive or negative, then on taking their              x ≥ y = 1/x ≤ 1/y
              reciprocals, the sign of inequality reverses
Replacement Set and Solution Set:
        The set, from which the value of the variable x is to be chosen, is called the replacement
         set.
        The subset of the replacement set, whose elements satisfy the given inequality is called
         the solution set.
Let the given inequality be x < 3 then:
1. If the replacement set = N, the set of natural numbers, then the solution set = {1, 2}
2. If the replacement set = Z or I, the set of integers, then the solution set = {2, 1, 0, −1, −2}
3. If the replacement set = R, the set of real numbers, then the solution set is {x: x ϵϵ R and x
< 3}
Representation of the solution on the number line
Convention
        A darkened circle on a number indicates that the number is also included in the solution
         set. (i.e. ≤ or ≥)
        A hollow circle on a number indicates that the number is not included in the solution set.
         (i.e. > or <)
                                                                                                      2
Combining Inequalities:
      Simplify the given inequality.
      Plot the solution set of each inequality on the number line.
      Study the solution sets and find out common points or regions of the given inequalities.