Question

usando o metodo da subtstituiçao resolva: {x - y =10 2x+3 y= 10}
{x= y+3 4x+y=-3}
{x+y=3 12X-9Y=-20}

Answer 1

x - y =10  ==> y = x - 10 ==> y = 8 - 10 ==> y = - 2
2x+3 y= 10

2x + 3(x-10) = 10 ==> 2x + 3x - 30 = 10

==> 5x = 10 + 30  ==> 5x = 40 ==> x = 8
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{x= y+3 ==> x = - 3 + 3 ==> x = 0
4x+y=-3

4(y+3) + y = - 3 ==> 4y + 12 + y = - 3 ==> 5y = - 3 - 12 => 5y=-15 => y = -3
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x+y=3  ==> y = 3 - x
12X-9Y=-20

12x - 9(3-x) = - 20 ==> 12x - 27 + 9x = - 20

21x = - 20 + 27 ==> 21x = 7 ==> x = 7/21

y = 3 - x ==> y = 3 - 7 ==> y = 63-7 ==> y = 56
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