CLASS-10
PROPERTIES OF INEQUATIONS

Properties of Inequations

(i) Adding the same number or expression to each side of an inequation does not change the inequality. e.r., x – 2 < 4

                    =>   x – 2 + 2 < 4 + 2

                    =>   x < 6

(ii) Subtracting the same number or expression from each side of an inequation does not change the inequality. e,g.,  x + 3 < 10

                    =>  x + 3 – 3 < 10 – 3

                    =>  x < 7


(iii) Multiplying (or dividing) each side of an inequation by the same positive number does not change

                          a

the inequality. e,g., ------ <  6

                          5

                           a

                   =>  ------- X 5  <  6 X 5

                           5

                   =>    a  <  30

(iv) Multiplying (or dividing) each side of an inequation by the same negative number reverse the inequality. e.g.,  - x < - 2

                   =>   x  >  2     [Multiplying both side by (- 1) ]

              And,  - 2x  <  8

                   =>    x > - 4     [Dividing both side by (- 2)]

Remarks : -  (ia < b  ó b  >  a

               (iia >  b  ó  b < a

          Thus,  x > 3 ó 3 < x

           And,  x < 5 ó 5 > x

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