Question

Solve the following simultaneous equations.

$3x+4y=18;4x+3y=17$

• A. $x=2$, $y=3$
• B. $x=-2$, $y=5$
• C. $x=4$, $y=3$
• D. $x=-2$, $y=-3$

Answer 1

The correct option is A $x=2$, $y=3$

The given equations are
$3x+4y=18$ ...(i)
$4x+3y=17$ ...(ii)

On multiplying (i) by 4 and (ii) by 3 and subtracting, we get
$12x+16y=72$
$\underset{–}{\underset{-}{1}2x\underset{-}{+}9y=\underset{-}{5}1}$
$7y=21$
$\Rightarrow y=3$

On putting $y=3$ in (i), we get
$3x+12=18\Rightarrow 3x=6\Rightarrow x=2$

$\therefore x=2,y=3$