Question

​ exercícios de fixação:

a)x-y=16
x+y=74




b)x+y=1
x-2y=1



c)2x=4x=-2
5x-3y=2
​

Answer 1

Resposta:

$a)\\ \\ ~~~~~~~~x~-y=16\\ +~~~~x+~y=74\\ ~~~~~~------\\ ~~~~~~2x~+~0=90\\ \\2x=90\\ \\ x=\frac{90}{2} \\ \\ x=45\\ \\ x+y=74\\ \\ 45+y=74\\ \\ y=74-45\\ \\ y=29\\ \\ S\left \{ {{45;29} {}} \}$

$b)\\ \\ x+y=1~~.(2)=2x+2y=2\\\\ ~~~~~~~~~~2x+2y=2\\+~~~~~~~x-~2y=1\\ ~~~~~~~~-------\\ ~~~~~~~~~~3x+~~0=3\\ \\ 3x=3\\ \\ x=\frac{3}{3} \\ \\ x=1\\ \\ x+y=1\\ \\ 1+y=1\\ \\ y=1-1\\ \\ y=0\\ \\ S\left \{ {{1;0} {}} \}$

$c)\\ \\ 2x-4x=-2~.(-1)=-2x+4x=2\\ \\ \\ -2x+4y=2\\ \\ ~~~~5x-3y=2\\ \\ logo\\ \\ 5x-3y=-2x+4y\\ \\ 5x+2x-3y-4y=0\\ \\ 7x-7y=0\\ \\ 7x=7y\\ \\ x=1=y\\ \\ S\left \{ {{x=1=y} {}} \}$