Solving linear equations inequalities algebra
To solving linear equations inequalities algebra means to find the value or values of the variable used in it.
Thus;
(i) to solve the inequality 2x + 4 > 6 means to find the variable x.
(ii) to solve the inequality 5 - 6y $\leq$ 3 means to find the value of y and so on.
The following are the rules must be followed for solving a given linear inequality.
Rule 1 : On transferring the positive term (in addition) from one side of an inequality to its other side, the sign of that transferred number changes to negative.
Examples :
4x + 6 > 7 ⇒ 4x > 7 - 6, 21 $\geq$ 2x + 8 ⇒ 21 - 8 $\geq$ 2x
7x + 4 $\leq$ 18 ⇒ 7x $\leq$ 18 - 4 and so on.
Rule 2: On On transferring the negative term (in subtraction) from one side of an inequality to its other side, the sign of that transferred number changes to positive .
Examples :
3x - 6 > 5 ⇒ 3x > 5 + 6, 42 $\geq$ 2x - 9 ⇒ 42 + 9 $\geq$ 2x
9x - 1 $\leq$ 20 ⇒ 9x $\leq$ 20 + 1 and so on.
Rule 3 : If each term of an equation be multiplied or divided by the same positive number, the sign of inequality remains the same.
Case I : If p is positive and x < y
x < y ⇒ px < py and $\left ( \frac{x}{p} \right )$ < $\left ( \frac{x}{p} \right )$
x > y ⇒ px > py and $\left ( \frac{x}{p} \right )$ > $\left ( \frac{x}{p} \right )$
x $\leq$ y ⇒ px $\leq$ py and $\left ( \frac{x}{p} \right )$ $\leq$ $\left ( \frac{x}{p} \right )$
x $\geq$ y ⇒ px $\geq$ py and $\left ( \frac{x}{p} \right )$ $\geq$ $\left ( \frac{x}{p} \right )$
For example x $\leq$ 5 ⇒ 3x $\leq$ 3 x 5 and
x $\geq$ 5 ⇒ 3x $\geq$ 3 x 5
Rule 4:If each term of an inequality be multiplied or divided by the same negative number, the sign of inequality will flip (reverse).
Case II : If p is negative,
x < y ⇒ -px > -py and $\left ( \frac{-x}{p} \right )$ > $\left ( \frac{-x}{p} \right )$
x > y ⇒ -px < -py and $\left ( \frac{-x}{p} \right )$ > $\left ( \frac{-x}{p} \right )$
x $\leq$ y ⇒ -px $\geq$ -py and $\left ( \frac{-x}{p} \right )$ $\geq$ $\left ( \frac{-x}{p} \right )$
x $\geq$ y ⇒ -px $\leq$ -py and $\left ( \frac{-x}{p} \right )$ $\leq$ $\left ( \frac{-x}{p} \right )$
Rule 5 : If the sign of the sides of an inequality are positive or negative, then while doing their reciprocals flip(reverse) the sign of inequality.
(i) x > y $\Leftrightarrow \frac{1}{x}$ < $\frac{1}{y}$
(ii) $x \geq y \Leftrightarrow \frac{1}{x} \leq \frac{1}{y}$
(iii) $x \leq y \Leftrightarrow \frac{1}{x} \geq \frac{1}{y}$ and so on.
11th grade math
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