
Step-by-step explanation
a line that passes throught the origin (0,0) is a line in the form

where k is the constant , rate of change or slope
so
Step 1
find the constant of the line:
to do that, check any coordiante and replace
a) pick up a coordinate from the line
Let
P(4,2)
so

replace

therefore, rewriting the function would be

I hope this helps you