Verified answer

1) 5x + 4y = 3

(3 ; - 3)

5 * 3 + 4 * (- 3) = 3

15 - 12 = 3

3 = 3

2) 9x - y = 70

(7 ; - 7)

9 * 7 - (- 7) = 70

63 + 7 = 70

70 = 70

3) x² + 4y = 0

(4 ; - 4)

4² + 4 * (- 4) = 0

16 - 16 = 0

0 = 0

4) x + |y| = 4

(2 ; - 2)

2 + |- 2| = 4

2 + 2 = 4

4 = 4