Question

Solve the following simultaneous equations.

(i) x + y = 4; 2x $-$ 5y = 1

Answer 1

$$\begin{gathered} \left(\mathrm{i}\right)x+y=4...\left(1\right) \\ 2x-5y=1...\left(2\right) \\ \mathrm{Multiplying}\mathrm{eq}\left(1\right)\mathrm{by}2,\text{we get:} \\ 2x+2y=8...\left(3\right) \\ \mathrm{Subtracting}\left(3\right)\mathrm{from}\left(2\right),\text{we get}: \\ 2x-5y=1 \\ 2x+2y=8 \\ \underline{\underline{\underline{---}}} \\ -7y=-7 \\ \therefore y=1 \\ \mathrm{Substituting}y=1\mathrm{in}\mathrm{equation}\left(1\right),\text{we get:} \\ x+1=4 \\ \Rightarrow x=3 \\ \therefore x=3,y=1\mathrm{is}\mathrm{the}\mathrm{solution}\mathrm{of}\mathrm{the}\mathrm{given}\mathrm{equation}s. \end{gathered}$$