Question

Find the values of the $x+y$ and $x-y$ from the examples given below without solving for x and y

$7x-5y=-1;5x-7y=-11$

• A. $-1$, $-5$
• B. $1$, $-5$
• C. $5$, $1$
• D. $5$, $-1$

Answer 1

The correct option is D $5$, $-1$

$\text{The given equations are}$

$7x-5y=-1$ ...(i)
$5x-7y=-11$ ...(ii)

On adding (i) and (ii), we get

$12x-12y=-12\Rightarrow x-y=-1$

On subtracting (ii) from (i), we get

$2x+2y=10\Rightarrow x+y=5$

$\therefore x+y=5andx-y=-1$