Question

A) {5x-2y=x-y-21 {5x=3y



B) {x/4-y/6= -1 {2x+y=6


C) {x-y/3=5+y {x/3-y=7+y

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Substitua por esses numeros:
A) (0,6)

B) (3,-3)

C) (-9,-15)

Answer 1

a)
5x - 2y = x - y
5x - x = 2y - y

4x = y
5x = 3y

(0,6) -----------4.0 ≠ 6 ------------ 0≠6
                       5.0 ≠ 3.6 --------- 0≠18

(3, -3) ---------4.3 ≠ -3 ------- 12 ≠ -3
                      5.3 ≠ 3.(-3) ---- 15 ≠ -9

(-9,-15) ------ 4.(-9) ≠ -15 ----- -36 ≠ 15
                      5.(-9) ≠ 3.(-15) ---- -45 = -45

b) x/4 - y/6 = -1
     2x + y = 6

(0,6)

0/4 - 6/6 = -1  -------- -1 = -1
2.0 + 6 = 6 -----------  6 = 6

(3,-3)
3/4 - (-3)/6 = -1
3/4 + 3/6 = -1
3/4 + 1/2 = -1
3.1/4 + 2.1/4 = -1.4/4
3 + 2 ≠ -4

2.3 - 3 = 6
6 - 3 ≠ 6

(-9,-15)

-9/4 - (-15)/6 = -1
-9/4 + 15/6 = -1 (MMC:12)
-9.3 + 15.2 = -1.12
-27 + 30 ≠ -12

c) x - y/3 = 5 + y

(0,6)
   0 - 6/3 = 5 + 6----- -2 ≠ 11
   0/3 - 6 = 7 + 6 -------- -6 ≠ 13

(3,-3)
  3 - (-3/3) = 5 -3 ------ 2 = 2
  3/3 - (-3) = 7 -3 ----- 1 + 3 = 4 ---------4 = 4

(-9,-15)
-9 - (-15/3) = 5 - 15 -------- -9 + 5 = -10 --------- -4 ≠ -10
-9/3 - (-15) = 7 -15 -------- -3 + 15 = -8 ------- 12 ≠ -8