- A student was set the following problem.
Use algebra to find the set of values of \(x\) for which
$$\frac { x } { x - 24 } > \frac { 1 } { x + 11 }$$
The student's attempt at a solution is written below.
$$\begin{gathered}
x ( x - 24 ) ( x + 11 ) ^ { 2 } > ( x + 11 ) ( x - 24 ) ^ { 2 }
x ( x - 24 ) ( x + 11 ) ^ { 2 } - ( x + 11 ) ( x - 24 ) ^ { 2 } > 0
( x - 24 ) ( x + 11 ) [ x ( x + 11 ) - x - 24 ] > 0
( x - 24 ) ( x + 11 ) \left[ x ^ { 2 } + 10 x - 24 \right] > 0
( x - 24 ) ( x + 11 ) ( x + 12 ) ( x - 2 ) > 0
x = 24 , x = - 11 , x = - 12 , x = 2
\{ x \in \mathbb { R } : - 12 < x < - 11 \} \cup \{ x \in \mathbb { R } : 2 < x < 24 \}
\end{gathered}$$
Line 3
There are errors in the student's solution.
- Identify the error made
- in line 3
- in line 7
- Find a correct solution to this problem.