Question

A)
$x + y = 10 \\ x - y = 5$
B)
$\frac{x}{6} = \frac{y}{4 } \\ 5x - 3y = 36$
C)
$4x - 4y = 5 \\ 3x - 3y = 7$
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Answer 1

Resposta:

ver na explicação

Explicação passo-a-passo:

$\left \{ {{x+y=10} \atop {x-y=5}} \right. \\2x=15\\x=\frac{15}{2}\\como \,\,\\x-y=5\\\frac{15}{2}-y=5\\15-2y=10\\15-10=2y\\5=2y\\y=\frac{5}{2}$

$\left \{ {{\frac{x}{6}=\frac{y}{4}} \atop {5x-3y=36}} \right. \\como\\x=\frac{6y}{4}=\frac{3y}{2}\\substituindo\,x\,na\,\,2\ª\\5*\frac{3y}{2}-3y=36\\\frac{15y}{2}-3y=36\\15y-6y=36*2\\9^{:9}y=36^{:9}*2\\ y=4*2\\y=8$

$\left \{ {{4x-4y=5} \atop {3x-3y=7}} \right. \\como\\4x=5+4y\\x=\frac{5+4y}{4}\\substiuindo\,\x\,\,na\,\,2\ª\\3*\frac{(5+4y)}{4}-3y=7\\\frac{(15+12y)}{4}-3y=7\\\frac{(15+12y-12y)}{4}=7\\15+12y-12y=7\\15\neq=7 (SI)$