Note that f(x) is a line in slope-intercept form, where a is the slope and b is the intercept.
Once you recognize that, you just need to know that, notationally, the –2 in front of f(x) means you multiply the whole thing by –2. So:
That’s still a line, but now the slope is –2a.
from Tumblr https://ift.tt/2mGBGF3