Question

Solve for x and y by method of cross multiplication:
$3x+2y+25=0$
$2x+y+10=0$

• A. $x=-5,y=-20$
• B. $x=5,y=-20$
• C. $x=-5,y=-20$
• D. $x=5,y=20$

Answer 1

The correct option is B $x=5,y=-20$

$3x+2y+25=0$
$2x+y+10=0$
By cross multiplication, we have
$\frac{x}{2\times 10-25\times 1}=\frac{y}{25\times 2-10\times 3}=\frac{1}{3\times 1-2\times 2}$
$\Rightarrow \frac{x}{20-25}=\frac{y}{50-30}=\frac{1}{3-4}$
$\Rightarrow \frac{x}{-5}=\frac{y}{20}=\frac{1}{-1}$
$\Rightarrow \frac{x}{-5}=\frac{1}{-1},\frac{y}{20}=\frac{1}{-1}$
$\therefore$ THe solution is $x=5,y=-20$