Question

resolva os sistemas a seguir usando o metodo da adição

a)4x-y=12
6x+2y=14

b)x/3+y/4=-1/2
x+y=3

Answer 1

a) $\left \{ {{4x-y=12} \atop {6x+2y=14}} \right.$

4x-y=12 *2

$+ \left \{ {{8x-2y=24} \atop {6x+2y=14}} \right.$

14x=38
$x= \frac{38}{14} \\ \\ x= \frac{19}{7}$

$4( \frac{19}{7})-y=12 \\ \\ \frac{76}{7}-y=12 \\ \\ y= \frac{76}{7} -12 \\ \\ y= \frac{76-84}{7} \\ \\ y= \frac{-8}{7}$

b)$\left \{ {{ \frac{x}{3} + \frac{y}{4}= \frac{-1}{2} } \atop {x+y=3}} \right.$

x+y=3
x=3-y
x=3-18
x=-15
$\frac{3-y}{3} + \frac{y}{4} = \frac{-1}{2} \\ \\ 12-4y+3y=-6 \\ \\ y=18$