Check if points A (3; 14), B (4; 13), C (-3; 0), D (0; 7) belong to the straight line 7x-3y + 21 = 0.

1. In order to determine without constructing whether a point belongs to the straight line 7x – 3y + 21 = 0, substitute its values ​​into the straight line and check whether the equality holds or not:

A) if the point has coordinates A (3; 14), then:

7 * 3 – 3 * 14 + 21 = 0;

21 – 42 + 21 = 0;

0 = 0, the point belongs to the line graph;

B) if the point has coordinates B (4; 13), then:

7 * 4 – 3 * 13 + 21 = 0;

28 – 39 + 21 = 0;

10 ≠ 0, the point does not belong to the graph of the straight line;

C) if the point has coordinates С (-3; 0), then:

7 * (- 3) – 3 * 0 + 21 = 0;

– 21 – 0 + 21 = 0;

0 = 0, the point belongs to the line graph;

D) if the point has coordinates D (0; 7), then:

7 * 0 – 3 * 7 + 21 = 0;

0 – 21 + 21 = 0;

0 = 0, the point belongs to the graph of the straight line.