• # question_answer Solve by elimination: $3x-y=7$ $2x+5y+1=0$

 $3x-y=7$                                                         ...(i) $2x+5y=-1$                                                                 ...(ii) Multiplying equation (i) by 5 and solving it with equation (ii), we get $_{\begin{smallmatrix} 15x\,-\,5y\,=\,35 \\ \overline{17x\,\,\,\,\,\,\,\,\,\,\,\,\,=\,34\,\,} \end{smallmatrix}}^{2x\,\,+\,\,5y\,\,=\,\,-1}$ (Adding) $\Rightarrow x=\frac{34}{17}=2$ Putting the value of x in (i), we have $3(2)-y=7$ $\Rightarrow 6-y=7\Rightarrow -y=7-6$ $\Rightarrow y=-1$ $\therefore \,\,x=2,y=-1$