# It is known that the graph of direct proportionality passes through the point A (3; 21).

It is known that the graph of direct proportionality passes through the point A (3; 21). Does this chart pass through point B (-7; -49); point C (-5; 3.5); point D (0.8; -5.6)?

Direct proportionality is the graph of the function y = k * x.

If it passes through the indicated points, then the ratio of the ordinate of the corresponding point to its abscissa is a constant number equal to the slope k.

Because the graph passes through point A, then 3 * k = 21, k = 7.

Point B:

-49 / (-7) = 7 = k, therefore, the graph goes through point B.

Point C:

3.5 / (-5) = -10 / 7 ≠ k, so point C does not belong to the graph.

Point D:

-5.6 / 0.8 = -7 ≠ k, therefore point D also does not belong to the graph.

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