Question

$$\frac{1}{x-7}-\frac{1}{x-5}=\frac{1}{x-13}-\frac{1}{x-11};$$

Answer

x=9

Solution


Multiply both sides by the Least Common Denominator: \((x-7)(x-5)(x-13)(x-11)\).
\[(x-5)(x-13)(x-11)-(x-7)(x-13)(x-11)=(x-7)(x-5)(x-11)-(x-7)(x-5)(x-13)\]
Simplify.
\[2{x}^{2}-48x+286=2{x}^{2}-24x+70\]
Cancel \(2{x}^{2}\) on both sides.
\[-48x+286=-24x+70\]
Add \(48x\) to both sides.
\[286=-24x+70+48x\]
Simplify  \(-24x+70+48x\)  to  \(24x+70\).
\[286=24x+70\]
Subtract \(70\) from both sides.
\[286-70=24x\]
Simplify  \(286-70\)  to  \(216\).
\[216=24x\]
Divide both sides by \(24\).
\[\frac{216}{24}=x\]
Simplify  \(\frac{216}{24}\)  to  \(9\).
\[9=x\]
Switch sides.
\[x=9\]