waecmaths question:
Solve the following equations $\begin{align} & 2x+3y=7 \\ & x+5y=0 \\\end{align}$
Option A:
x = 5, y = –1
Option B:
$x=\tfrac{1}{5},y=-1$
Option C:
$x=\tfrac{1}{5},y=-1$
Option D:
$x=-5,y=1$
waecmaths solution:
$\begin{align} & 2x+3y=7---(i) \\ & x+5y=0---(ii) \\ & x=-5y \\ & \text{Substitute }-5y\text{ for }x\text{ into }(i) \\ & 2(-5y)+3y=7 \\ & -10y+3y=7 \\ & -7y=7 \\ & y=-1 \\ & \therefore x=-5(-1)=5 \\ & x=5,\text{ }y=-1 \\\end{align}$
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