Use the formula to define a linear function that is parallel to the line y = 2x + 9 and passes through the origin.

Graphs of linear functions are parallel if in the linear equations defining them they have the same coefficient at x. In this case, this is the number 2. Thus, all lines parallel to a given one are expressed by an equation of the form: y = 2x + b, where in a certain number.

The sought linear function must pass through the origin. Substitute the coordinates of the point (0; 0) into the equation of the linear function and find in:

0 = 2 * 0 + b;

h = 0.

Thus, a function whose graph passes through the origin and is parallel to the graph y = 2x + 9 is y = 2x.

Answer: y = 2x.