Situation 1:

f
(
x
)
=
14
x
−
12
f(x)=14x−12
g
(
x
)
=
7
x
2
−
3
x
−
11
g(x)=7x2−3x−11

Mark is asked to find
(
g
−
f
)
(
x
)
.
(g−f)(x).
This is his work:

14
x
−
12
−
7
x
2
−
3
x
−
11
−
7
x
2
+
11
x
+
23
14x−12−7x2−3x−11−7x2+11x+23

Find Mark's mistakes (there are more than one). Explain what he did wrong and how to fix it.