Question

Solve for x and y using substitution method:

$\frac{1}{2x}-\frac{1}{y}=-1$

$\frac{1}{x}+\frac{1}{2y}=8$

(Given: $x\ne 0andy\ne 0)$

• A. $x=\frac{1}{6},y=\frac{1}{4}$
• B. $x=\frac{1}{7},y=\frac{1}{2}$
• C. $x=\frac{1}{8},y=\frac{1}{3}$
• D. $x=\frac{3}{4},y=\frac{5}{4}$

Answer 1

The correct option is A

$x=\frac{1}{6},y=\frac{1}{4}$

We have

$\frac{1}{2x}-\frac{1}{y}=-1\dots .\left(1\right)$

$\frac{1}{x}+\frac{1}{2y}=8\dots .\left(2\right)$

From equation (1), $\frac{1}{2x}=-1+\frac{1}{y}$

$\Rightarrow \frac{1}{2x}=\frac{(-y+1)}{y}$

$\Rightarrow 2x=\frac{y}{(-y+1)}$

$\Rightarrow x=\frac{y}{(-2y+2)}$

Substituting $x=\frac{y}{(-2y+2)}$ in equation (2),

$\frac{(-2y+2)}{y}+\frac{1}{2y}=8$

$\Rightarrow \frac{(-4y+4+1)}{2y}=8$

$\Rightarrow -4y+4+1=16y$

$\Rightarrow 20y=5$

$\Rightarrow y=\frac{1}{4}$

Substituting $y=\frac{1}{4}$ in equation (1),

$\Rightarrow \frac{1}{2x}-4=-1$

$\Rightarrow \frac{1}{2x}=3$

$\Rightarrow x=\frac{1}{6}$