Loosely speaking, a rational equation is an equation containing rational expressions.

When a rational equation contains only one fractional term, like

\dfrac{2}{x} = 1 ,

we can multiply both sides of the equation by the denominator to remove the fraction. This leaves us with a linear equation, which we can then solve using the addition and multiplication principles.

Before we proceed, we note that x=0 cannot be a solution. This is because if x=0 then the rational term would be \dfrac{2}{0}, which is undefined because it has a zero denominator.

To solve the equation, we multiply both sides by the denominator {\color{blue} x} to get rid of the fraction: \begin{align} \require{cancel} \dfrac{2}{x} & = 1 \\ {\color{blue} x}\cdot \dfrac{2}{x} & = {\color{blue} x} \cdot 1\\ {\cancel{x}}\cdot \dfrac{2}{\cancel{x}} & = {x} \cdot 1\\ 2&=x. \end{align}

Since x=2 is different from x=0 , we can accept it as a solution. Thus, the solution is x=2.

FLAG

Find the solution to \dfrac {1} {x-2} = 5 .

EXPLANATION

First, note that x=2 cannot be a solution. This is because if x=2, then the rational term would be \dfrac{1}{0}, which is undefined because it has a zero denominator.

To solve the equation, we first multiply both sides by the denominator (x-2) to get rid of the fraction:

\begin{align*} \require{cancel} \dfrac {1} {x-2}& = 5\\ (x-2) \cdot \dfrac {1} {x-2} &= (x-2) \cdot 5\\ \cancel{(x-2)} \cdot \dfrac {1} {\cancel{x-2}} &= 5x-10 \\ 1 &= 5x-10 \end{align*}

Then, we apply the addition and multiplication principles, as usual:

\begin{align*} \require{cancel} 1 &= 5x-10 \\ 1+10 &= 5x-10+10 \\ 11 &= 5x \\ \dfrac{11}{5} &= \dfrac{5x}{5} \\ \dfrac{11}{5} &= x \end{align*}

Since x=\dfrac{11}{5} is different from x=2 , we can accept it as a solution. Thus, the solution is x=\dfrac{11}{5}.

FLAG

Solve the equation $\dfrac {12} {x} = - 4 .$

a
$x=-4$
b
$x=-2$
c
$x=3$
d
$x=4$
e
$x=-3$

Solve the equation $\dfrac{4}{5x}=2.$

a
$\dfrac{3}{4}$
b
$\dfrac{5}{8}$
c
$\dfrac{2}{5}$
d
$\dfrac{8}{5}$
e
$\dfrac{5}{2}$

Solve the equation $\dfrac {3} {x-4} = 2 .$

a
$x = \dfrac{13}{3}$
b
$x = \dfrac{14}{3}$
c
$x = \dfrac{11}{2}$
d
$x = \dfrac{5}{2}$
e
$x = \dfrac{3}{2}$

Solve \dfrac {3x} {x+1} = 2 .

EXPLANATION

First, note that x=-1 cannot be a solution since division by 0 is undefined.

To solve the equation, we first multiply both sides by the denominator (x+1) to get rid of the fraction:

\begin{align*} \require{cancel} \dfrac {3x} {x+1}& = 2\\ (x+1) \cdot \dfrac {3x} {x+1} &= (x+1) \cdot 2\\ \cancel{(x+1)} \cdot \dfrac {3x} {\cancel{x+1}} &= 2x+2 \\ 3x &= 2x+2 \end{align*}

Then, we apply the addition principle:

\begin{align*} \require{cancel} 3x &= 2x+2 \\ 3x-2x &= 2x+2-2x \\ x &= 2 \end{align*}

Since x = 2 is different from x=-1 , we can accept it as a solution. Thus, the solution is x=2.

FLAG

Solve the equation $\dfrac{x}{x-5} = 6.$

a
$x=\dfrac{7}{6}$
b
$x=-8$
c
$x=6$
d
$x=\dfrac{4}{5}$
e
$x=-\dfrac{3}{2}$

Solve the equation $2 = \dfrac{5x + 1}{x+1}.$

a
$x=-6$
b
$x=\dfrac{1}{2}$
c
$x=8$
d
$x=\dfrac{1}{3}$
e
$x=-\dfrac{2}{5}$

Solve the equation \dfrac {1} {2x+1} = 2 .

EXPLANATION

First, note that the denominator 2x+1 cannot be zero, since division by 0 is undefined. Therefore we cannot have 2x+1=0, which means x=-\dfrac{1}{2} cannot be a solution.

To solve the equation, we first multiply both sides by the denominator (2x+1) to get rid of the fraction:

\begin{align*} \require{cancel} \dfrac {1} {2x+1}& = 2 \\[5pt] (2x+1) \cdot \dfrac {1} {2x+1} &= (2x+1) \cdot 2 \\[5pt] \cancel{(2x+1)} \cdot \dfrac {1} {\cancel{2x+1}} &= 4x+2 \\[5pt] 1 &= 4x+2 \end{align*}

Then, we apply the addition and multiplication principles, as usual:

\begin{align*} \require{cancel} 1 &= 4x+2 \\[5pt] 1-2 &= 4x+2-2 \\[5pt] -1 &= 4x \\[5pt] \dfrac{-1}{4} &= \dfrac{4x}{4} \\[5pt] -\dfrac{1}{4} &= x \end{align*}

Since x = -\dfrac{1}{4} is different from x=-\dfrac{1}{2} , we can accept it as a solution. Thus, the solution is x=-\dfrac{1}{4}.

FLAG

Solve the equation $\dfrac{x}{5x - 3} = 9.$

a
$x= -\dfrac{14}{3}$
b
$x=-\dfrac{42}{13}$
c
$x=\dfrac{27}{44}$
d
$x= \dfrac{15}{11}$
e
$x= \dfrac{3}{5}$

Solve the equation $\dfrac{19x - 7}{3x-3} = 3.$

a
$x=\dfrac{4}{7}$
b
$x=\dfrac{7}{9}$
c
$x=-\dfrac{2}{13}$
d
$x=-\dfrac{1}{2}$
e
$x=-\dfrac{1}{5}$
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