Consider the rational equation

\dfrac{12}{x+3} = \dfrac{2}{x-2}.

Recall that when the equation consists of a single rational expression on each side, like the one above, then the easiest way to solve it is usually to use cross-multiplication.

However, before we start, note that x=-3 and x=2 cannot be solutions. This is because when x=-3, we get a zero in the denominator on the left-hand side, and when x=2, we get a zero in the denominator on the right-hand side.

With this in mind, let's solve the equation. First, we cross-multiply:

\begin{align} \dfrac{\color{red}12}{\color{blue}x+3} &= \dfrac{\color{blue}2}{\color{red}x-2} \\[5pt] {\color{red}12}\cdot{\color{red}(x-2)} &= {\color{blue}(x+3)}\cdot{\color{blue}2} \\[5pt] 12x-24 &= 2x+6 \end{align}

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

\begin{align} 12x-24 &= 2x+6 \\[5pt] 12x-24-2x &= 2x+6-2x \\[5pt] 10x-24 &= 6 \\[5pt] 10x-24+24 &= 6+24 \\[5pt] 10x &= 30 \\[5pt] \dfrac{10x}{10} &= \dfrac{30}{10} \\[5pt] x &= 3 \end{align}

Since x=3 is different from x=-3 and x=2, we accept it as a solution. Thus, the solution is x=3.

FLAG

Solve \dfrac{2}{1-2k}=-\dfrac{4}{3k}.

EXPLANATION

First, note that k=\dfrac{1}{2} and k=0 cannot be solutions since division by 0 is undefined.

To solve the equation, we move the negative sign onto the numerator of the fraction and then apply cross-multiplication:

\eqalign{ \dfrac{2}{1-2k}&=-\dfrac{4}{3k}\\[5pt] \dfrac{2}{1-2k}&=\dfrac{-4}{3k}\\[5pt] 2 \cdot 3k &= (-4) \cdot (1-2k)\\[5pt] 6k&=-4+8k }

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

\eqalign{ 6k&=-4+8k\\[5pt] 6k-8k &=-4+8k-8k\\[5pt] -2k&=-4\\[5pt] \dfrac{-2k}{-2} &= \dfrac{-4}{-2} \\[5pt] k &= 2 }

Since k = 2 is different from k=0 and k=\dfrac{1}{2} , we can accept it as a solution. Thus, the solution is k=2.

FLAG

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

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

Solve for $y$ where $\dfrac {9} {y-7} = \dfrac {6} {y}.$

a
$y= -7$
b
$y = 7$
c
$y = -5$
d
$y = -14$
e
$y = 0$

Solve for $z$ where $\dfrac{3}{4z}=\dfrac{2}{z+10}.$

a
b
c
d
e

Solve for x where -\dfrac{3}{2x}=\dfrac{2}{x+7}.

EXPLANATION

First, note that x=0 and x=-7 cannot be solutions since division by 0 is undefined.

To solve the equation, we move the negative sign onto the numerator of the fraction and then apply cross-multiplication:

\eqalign{ -\dfrac{3}{2x}&=\dfrac{2}{x+7}\\[5pt] \dfrac{-3}{2x}&=\dfrac{2}{x+7}\\[5pt] (-3) \cdot (x+7) &=2x \cdot (2) \\[5pt] -3x - 21&= 4x }

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

\eqalign{ -3x - 21&= 4x\\[5pt] -3x -21 + 3x&=4x + 3x\\[5pt] -21&=7x\\[5pt] \dfrac{-21}{7}&=\dfrac{7x}{7} \\[5pt] -3 &= x }

Since x = - 3 is different from x=0 and x=-7 , we can accept it as a solution. Thus, the solution is x= -3.

FLAG

Solve for $y$ where $-\dfrac{3}{2y+3} = \dfrac{2}{y}.$

a
b
c
d
e

Solve for $s$ where $\dfrac{4}{s}=-\dfrac{6}{s+2}.$

a
$s=\dfrac{4}{5}$
b
$s=-4$
c
$s=\dfrac{1}{4}$
d
$s=-\dfrac{4}{5}$
e
$s=4$

Solve for $x$ where $-\dfrac{3}{x}=\dfrac{2}{x+5}.$

a
b
c
d
e

Solve the equation \dfrac{2}{4x+12}=\dfrac{2}{x+3}.

EXPLANATION

First, note that x=-3 cannot be a solution since division by 0 is undefined.

To solve the equation, we first apply cross-multiplication:

\eqalign{ \dfrac{2}{4x+12} &= \dfrac{2}{x+3} \\ 2 \cdot (x+3) &= (4x+12) \cdot 2 \\ 2x + 6 &= 8x + 24 }

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

\eqalign{ 2x + 6 &= 8x + 24 \\ 2x + 6-24 &= 8x + 24-24 \\ 2x-18 &= 8x \\ 2x-18-2x &= 8x-2x \\ -18 &= 6x \\ \dfrac{-18}{6} &= \dfrac{6x}{6} \\ -3 &= x }

Since x=-3 cannot be a solution, the equation has no solutions.

FLAG

Solve for $x$ where $\dfrac{1}{x-2} = \dfrac{2}{x+4}.$

a
b
c
d
e

Solve for $x$ where $-\dfrac{1}{2x+6} = \dfrac{5}{x+14}.$

a
b
c
d
e

Solve the equation $\dfrac{2}{3x+12}=\dfrac{2}{x+4}.$

a
$x = 4$
b
$x=-\dfrac{3}{2}$
c
No solutions
d
$x = 5$
e
$x=-2$
Flag Content
Did you notice an error, or do you simply believe that something could be improved? Please explain below.
SUBMIT
CANCEL