a) Given f(x)=(x=4)(x-2), write equtions for -f(x) and f(-x)

b)Sketch the tree graphs on the same set of axes
c) State the domian and range of each function

Firstly f(x)=(x=4)(x-2) is wrong you have two = signs. I'm assuming it's a + or another -.

a) Well, you know f(x), so -f(x) just has a - in front of it.

f(-x) means put -x in everywhere you see x

b) f(x), -f(x) and f(-x) are all of the form y = ax^2+bx+c which is a parabola in graph terms.

c) The domain is all the x-values, and the range is all the y-values

For any line the domain is -inf to inf
and the range is also -inf to inf

For a parabola the domain is -inf to inf
the range is either;
+ve x^2 --> inf to turing point
-ve x^2 --> turning point to -inf

Ok, hope that helps