Question

2x − y = 1
7x − 2y = −7

Answer 1

$$\begin{gathered} \mathrm{Given}:\hspace{0.17em}2x-y=1 \\ 7x-2y=-7 \\ \mathrm{Using}\mathrm{Crammer}\text{'}\mathrm{s}\mathrm{Rule},\mathrm{we}\mathrm{get} \\ \mathrm{D}=\left|2-1 \\ 7-2\right|=-4+7=3 \\ {\mathrm{D}}_1=\left|1-1 \\ -7-2\right|=-2-7=-9 \\ {\mathrm{D}}_2=\left|21 \\ 7-7\right|=-14-7=-21 \\ \mathrm{Now}, \\ \mathrm{x}=\frac{{\mathrm{D}}_1}{\mathrm{D}}=\frac{-9}{3}=-3 \\ \mathrm{y}=\frac{{\mathrm{D}}_2}{\mathrm{D}}=\frac{-21}{3}=-7 \\ \therefore \mathrm{x}=-3\mathrm{and}\mathrm{y}=-7 \end{gathered}$$