Question

Comente as seguintes soluções:

a) 13x-4x=27
b) x+y=4
{
x-y=8​

Answer 1

Resposta:

a) x = 3

b) x = 6; y = -2

Explicação passo-a-passo:

a) $13x-4x=27$

$9x=27\\\frac{9x}{9}=\frac{27}{9}\\x=3$

b) $\left \{ {{x+y=4} \atop {x-y=8}} \right$

$=\left \{ {{x=4-y} \atop {x-y=8}} \right\\=\left \{ {{x=4-y} \atop {(4-y)-y=8}} \right\\=\left \{ {{x=4-y} \atop {4-2y=8}} \right\\=\left \{ {{x=4-y} \atop {4-2y-4=8-4}} \right\\=\left \{ {{x=4-y} \atop {-2y=4}} \right\\=\left \{ {{x=4-y} \atop {\frac{-2y}{-2}=\frac{4}{-2}}} \right\\=\left \{ {{x=4-y} \atop {y=-2} \right$

$y=-2$

$x=4-y\\x=4-(-2)\\x=4+2\\x=6$