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Introduction to Inequalities





What is inequalities

  • In mathematics, an inequality is a relation that holds between two values when they are different
  • Solving linear inequalities is very similar to solving linear equations, except for one small but important detail: you flip the inequality sign whenever you multiply or divide the inequality by a negative

Symbols used in inequalities

  • The symbol < means less than. The symbol > means greater than.
  • The symbol < with a bar underneath means less than or equal to. Usually this is written as $\leq$
  • The symbol > with a bar underneath means greater than or equal to. Usually this is written as $\geq$
  • The symbol $\neq$ means the quatities on left and right side are not equal

Examples
  • a < b means a is less then b or b is greater a
  • $a  \leq b$ means a is less then or equal to b
  • a > b means a is greater than b
  • $a \geq b$ means a is greater or equal to b

Things are which are safe to do in inequality which does not change in direction

  • addition of same number on both sides
    $a > b $
    => $a+c > b +c $
  • Substraction of same number on both sides
    $a > b$
    =>$a-c > b-c$
  • Multipication/Division by same positive number on both sides
    $a > b$
    if c is positive number then
    $ac > bc$
    or
    $\frac {a}{c} > \frac {b}{c}$

Things which changes the direction of the inequality

  • swapping the left and right sides
  • Multiplication/Division by negative number on both sides
  • Dont multiple by variable whose values you dont know as you dont know the nature of the variable

Concept Of Number line

  • A number line is a horizontal line that has points which correspond to numbers. The points are spaced according to the value of the number they correspond to; in a number line containing only whole numbers or integers, the points are equally spaced.
    Number line
  • It is very useful in solving problem related to inequalities and also representing it
    Suppose x >2(1/ 3), this can represent this on number line like that
    inequality using number line


Linear Inequation in One Variable

A equation of the form
$ ax+b > 0 $
or
$ax+b \geq 0$
or
$ax+b< 0$
or
$ax+b \leq 0$
are called the linear equation in One Variable
Example:
  • $x-2 < 0 $
  • $3x +10 > 0$
  • $10x-17 \geq 0$

Linear Inequation in Two Variable

A equation of the form
$ax+by > c$
or
$ax+by \geq c$
or
$ax+by< c $
or
$ax+by \leq c$
are called the linear equation in two Variable
Example:
  • $x-2y < 0 $
  • $3x +10y > 0 $
  • $10x-17y \geq 0$


Related Topics


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Class 11 Maths Class 11 Physics





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