Let's compare f(x) and g(x):
f(x) = x + 4
g(x) = x - 3
Both f(x) and g(x) are linear functions in slope-intercept form. They both have the same slope, with the only difference being their y-intercept.
Therefore, we can see that g(x) is a vertical translation of f(x) by -7 units. In other words, g(x) is translated 7 units down from f(x).
In general, if f(x) is a parent function, and g(x) is a transformation of f(x) written as g(x) = f(x) + a, then a describes a vertical translation of f(x).
- If a is positive, it's translated "up".
- If a is negative, it's translated "down".
Therefore, we can calculate the specific translation algebraically:
- g(x) = f(x)+ a
- x - 3 = x + 4 + a
- -7 = a
Therefore, we can represent g(x) as f(x) - 7.
Just an added note, but translations are a type of transformation called a "rigid" transformation, which you will see a lot more in Geometry. A rigid transformation is one that preserves the congruency of the shape, hence the term rigid.