If f(3) = 15 and f(5) = 45, which of the following could be f(x)?
can anyone explain this one for me?

For the equations below which statement is true ?

The figure shows triangle def and line segment bc, which is parallel to ef: triangle def has a point b on side de and point c on side df. the line bc is parallel to the line ef. part a: is triangle def similar to triangle dbc? explain using what you know about triangle similarity. part b: which line segment on triangle dbc corresponds to line segment ef? explain your answer. part c: which angle on triangle dbc corresponds to angle f? explain your answer. asap

If f(x) = 4x - 3 and g(x) = x + 4, find (f - g) (x)