Im failing.. please help me.. Consider the arithmetic sequence.

-9, -2, 5, 12, . . .

Given that the sequence is represented by the function f(n), what are the values of f(1) and the common difference?

A.
f(1) = -2
Common difference : -7
B.
f(1) = -2
Common difference : 7
C.
f(1) = -9
Common difference : 7
D.
f(1) = -9
Common difference : -7

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