Question

Find the value of z where
$z=\frac{5x+9y+4z}{3y+6}$; $x=1$ and $y=-1$

• A. $z=-4$
• B. $z=-3$
• C. $z=3$
• D. $z=4$

Answer 1

The correct option is D $z=4$

Substitute the value of x and y in the expression on the RHS of the given equation.

$z=\frac{5x+9y+4z}{3y+6}$

$z=\frac{5\times 1+9\times (-1)+4z}{3\times (-1)+6}$

Now, solving this equation for $z$, we get

$\Rightarrow z=\frac{-4+4z}{-3+6}$

$\Rightarrow z=\frac{-4+4z}{3}$

$\Rightarrow 3z=-4+4z$

$\Rightarrow 3z-4z=-4$

$\Rightarrow -z=-4$

$\therefore z=4$