the functional equation of the line is f (x)=a*x+b
you have already a: -4 -->f (x)=-4 x+b
Now you can use the point (3;-3)
3 is the x-coordinate and -3 the f (x)-coordinate
--> -3 = -4*(3) + b Now you can solve it
-3 = -12+b (+12)
b = 9
ANSWER: f (x) = -4x + 9
