Let's consider the following inequality:

7x -2 < 5x - 18

As usual, we solve the inequality just like we would solve an equation.

First, we apply the addition principle. We start by subtracting 5x from both sides:

\begin{align} 7x - 2 &< 5x - 18 \\[5pt] 7x - 2 - 5x &< 5x - 18 - 5x \\[5pt] 2x - 2 &< - 18 \end{align}

Then, we add 2 to both sides:

\begin{align} 2x - 2 &< - 18 \\[5pt] 2x - 2 + 2&< - 18+2 \\[5pt] 2x &< - 16 \\[5pt] \end{align}

Finally, we use the multiplication principle, dividing both sides by 2{:}

\begin{align} \require{cancel} 2x &< - 16 \\[5pt] \dfrac{2x}{2} &< \dfrac{-16}{2} \\[5pt] x &< -8 \\[5pt] \end{align}

Therefore, the solution is x < -8.

FLAG

Solve the inequality 5x+13 \ge 3x-7 and sketch the solution on the number line.

EXPLANATION

We solve the inequality just like we would solve an equation.

First, we apply the addition principle:

\begin{align} 5x+13 &\ge 3x-7 \\[5pt] 5x+13-3x &\ge 3x-7-3x \\[5pt] 2x+13 &\ge -7 \\[5pt] 2x+13-13 &\ge -7-13 \\[5pt] 2x &\ge -20 \\[5pt] \end{align}

Then, we use the multiplication principle:

\begin{align} 2x &\ge -20 \\[5pt] \dfrac{2x}{2} &\ge \dfrac{-20}{2} \\[5pt] x &\ge -10 \end{align}

Therefore, the solution is x \ge -10.

Our solution can be expressed using a number line, as shown below.

FLAG

Solve the inequality $2g + 12 \le 10 - 7g.$

a
$g \ge \dfrac{2}{9}$
b
$g \le -\dfrac{22}{5}$
c
$g \le -\dfrac{2}{9}$
d
$g \ge -\dfrac{2}{5}$
e
$g \le \dfrac{2}{9}$

Which of the following number lines gives the solution to $-6b + 36 > 4b - 4?$

a
b
c
d
e

Now, let's solve an inequality that contains a rational expression:

\dfrac{2y-1}{3} \lt 5

First, we clear the rational expression by multiplying both sides by 3{:}

\begin{align} \require{cancel} \dfrac {2y-1} {3} &\lt 5 \\[5pt] 3\cdot \left (\dfrac {2y-1}{3}\right) &\lt 3 \cdot 5 \\[5pt] \cancel{3}\cdot\left (\dfrac {2y-1} {\cancel{3}}\right) &\lt 15 \\[5pt] 2y-1 & \lt 15 \end{align}

Then, we apply the addition and multiplication principles:

\begin{align} 2y-1 &\lt 15 \\[5pt] 2y-1+1 &\lt 15+1 \\[5pt] 2y &\lt 16 \\[5pt] \dfrac{2y}{2} &\lt \dfrac{16}{2} \\[5pt] \dfrac{\cancel{2}y}{\cancel{2}} &\lt \dfrac{16}{2} \\[5pt] y &\lt 8 \end{align}

Therefore, the solution is y < 8.

FLAG

Solve the inequality \dfrac{2-5y}{3} \le 4.

EXPLANATION

First, we clear the rational expression by multiplying both sides by 3{:} \begin{align*} \require{cancel} \dfrac{2-5y}{3} &\le 4 \\[5pt] 3\cdot \left(\dfrac {2-5y} {3}\right) &\le 3\cdot 4 \\[5pt] \cancel{3}\cdot \left(\dfrac {2-5y} {\cancel{3}}\right) &\le 3\cdot 4 \\[5pt] 2-5y &\le 12 \end{align*}

Then, we apply the addition and multiplication principles.

Remember, when we divide an inequality by a negative number, we need to flip the inequality sign:

\begin{align*} 2-5y &\le 12 \\[5pt] 2-5y-2 &\le 12-2 \\[5pt] -5y &\le {10} \\[5pt] \dfrac{-5y}{-5} &\,\,{\color{red}{\ge}}\,\, \dfrac{10}{-5} \\[5pt] \dfrac{\cancel{-5}y}{\cancel{-5}} &\ge -2 \\[5pt] y &\ge -2 \end{align*}

Therefore, the solution is y \ge -2.

FLAG

Solve the inequality $\dfrac{7x-5}{3} \gt 3.$

a
$x < 2$
b
$x > 3$
c
$x < -2$
d
$x < -3$
e
$x > 2$

Solve the inequality $\dfrac{7-3x}{2} \gt 2.$

a
$x\gt -1$
b
$x\lt 1$
c
$x\gt 1$
d
$x\lt -1$
e
$x\gt 3$

Which of the following number lines gives the solution to $\dfrac{9x+1}{2} \geq 5?$

a
b
c
d
e

Solve the inequality 4y -1 > \dfrac {5y - 2} {3}.

EXPLANATION

First, we clear the rational expression by multiplying both sides by 3{:}

\begin{align*} \require{cancel} 4y -1 &> \dfrac {5y - 2} {3} \\[5pt] 3\cdot(4y -1) &> 3 \cdot \left(\dfrac{5y - 2}{3}\right) \\[5pt] 3\cdot(4y -1) &> \cancel{3} \cdot \left(\dfrac{5y - 2}{\cancel{3}}\right) \\[5pt] 3\cdot(4y -1) &> 5y-2 \\[5pt] 12y-3 &> 5y-2 \end{align*}

Next, we use the addition principle:

\eqalign{ 12y-3 &> 5y-2 \\[5pt] 12y-3-5y &> 5y-2-5y \\[5pt] 7y-3 &> {-2} \\[5pt] 7y-3 +3 &> {-2} +3 \\[5pt] 7y &> {1} }

Finally, we use the multiplication principle:

\begin{align*} 7y &> {1} \\[5pt] \dfrac{7y}{7} &> \dfrac{1}7 \\[5pt] \dfrac{\cancel{7}y}{\cancel{7}} &> \dfrac{1}{7} \\[5pt] y &> \dfrac{1}{7} \end{align*}

Therefore, the solution is y > \dfrac17.

FLAG

Solve the inequality $ \dfrac {1-6x} {3} \geq 2x.$

a
$x \leq -\dfrac {1} {12}$
b
$x \geq \dfrac {1} {12}$
c
$x \leq \dfrac {1} {12}$
d
$x \geq -\dfrac {1} {12}$
e
$x \geq \dfrac {1} {6}$

Solve the inequality $5y + 2 \le \dfrac {3y - 1} {2}.$

a
$y \ge \dfrac{7}{5}$
b
$y \le \dfrac{5}{7}$
c
$y \le -\dfrac{7}{5}$
d
$y \le -\dfrac{5}{7}$
e
$y \ge -\dfrac{5}{7}$

Solve the inequality $\dfrac{1-3a}{2} < 4a - 2.$

a
$a > \dfrac{3}{5}$
b
$a < \dfrac{3}{5}$
c
$a > \dfrac{5}{11}$
d
$a \gt \dfrac{3}{11}$
e
$a < \dfrac{5}{11}$

Finally, let's consider an inequality that contains rational expressions on both sides:

\dfrac{x+1}{4} \leq \dfrac{x}{2}

First, we clear the rational expressions by cross-multiplying:

\begin{align*} \dfrac{x+1}{\color{red}{4}} &\leq \dfrac{x}{\color{blue}2}\\[5pt] {\color{blue}2}\cdot (x+1) &\leq {\color{red}{4}} \cdot x \\[5pt] 2x + 2 &\leq 4x \end{align*}

Next, we use the addition principle:

\begin{align*} 2x + 2 &\leq 4x \\[5pt] 2x + 2 - 2x &\leq 4x - 2x \\[5pt] 2 &\leq 2x \end{align*}

Finally, we use the multiplication principle:

\begin{align*} \require{cancel} 2 &\leq 2x \\[5pt] \dfrac{2}{2} &\leq \dfrac{2x}{2} \\[5pt] \dfrac{2}{2} &\leq \dfrac{\cancel{2}x}{\cancel{2}} \\[5pt] 1 &\leq x \\[5pt] x&\geq 1 \end{align*}

Therefore, the solution is x\geq 1.

FLAG

Solve the inequality \dfrac{3a-2}{5} > \dfrac{4+6a}{2}.

EXPLANATION

First, we clear the rational expressions by cross-multiplying:

\begin{align*} \dfrac{3a-2}{5} &> \dfrac{4+6a}{2} \\[5pt] 2\cdot (3a-2) &> 5 \cdot (4+6a) \\[5pt] 6a -4 &> 20 +30a \end{align*}

Next, we use the addition principle:

\begin{align*} 6a -4 &> 20 +30a \\[5pt] 6a -4 -6a &> 20 +30a -6a \\[5pt] -4 &> 20+24a \\[5pt] -4-20 &> 20 +24a-20 \\[5pt] -24 &> {24}a \end{align*}

Finally, we use the multiplication principle:

\begin{align*} \require{cancel} -24 &> 24a \\[5pt] \dfrac{-24}{24} &> \dfrac{24a}{24} \\[5pt] -1&> \dfrac{\cancel{24}a}{\cancel{24}} \\[5pt] -1 &> a \\[5pt] a &< {-1} \end{align*}

Therefore, the solution is a < -1.

FLAG

Solve the inequality $\dfrac{4x+7}{3} \geq \dfrac{5x}{2}.$

a
$x \geq -2$
b
$x \leq -1$
c
$x \geq 2$
d
$x \geq 1$
e
$x \leq 2$

Solve the inequality $\dfrac{x+10}{4} > \dfrac{6-2x}{5}.$

a
$x < 2$
b
$x < 1$
c
$x > -1$
d
$x > 2$
e
$x > -2$
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