57/(x + y) + 6/(x – y) = 5 38/(x + y) + 21/(x – y) = 9 Solution: Let  substitute $\frac{1}{\left( x+y \right)}=u$ and $\frac{1}{\left( x-y \right)}=v$, \[57u\text{ }+\text{ }6v\text{ }=\text{ }5\]...

\[\mathbf{9}.\] \[\mathbf{5}/\left( \mathbf{x}\text{ }+\text{ }\mathbf{y} \right)\text{ }\text{ }\mathbf{2}/\left( \mathbf{x}\text{ }-\mathbf{y} \right)\text{ }=\text{ }-\mathbf{1}\]...

\[\mathbf{7}.\]\[~\mathbf{x}\text{ }+\text{ }\mathbf{ay}\text{ }=\text{ }\mathbf{b}\] \[\mathbf{ax}\text{ }+\text{ }\mathbf{by}\text{ }=\text{ }\mathbf{c}\] \[\mathbf{8}.\] \[\mathbf{ax}\text{...

2x + y = 35, 3x + 4y = 65 Solution: Given \[\mathbf{2x}\text{ }+\text{ }\mathbf{y}\text{ }\text{ }-\mathbf{35}\text{ }=\text{ }\mathbf{0}\] \[\mathbf{3x}\text{ }+\text{ }\mathbf{4y}\text{ }\text{...