The sketch below shows the function y = f(x) and a transformation, labelled C. Write down the equation of the translated curve C in function form.
How I found out the function:
But it says the answer is -2f(2x).
What did I do wrong? Thank You and Help is Appreciated.
You just forgot to reflect your graph about the $x$-axis. Hence, your answer differ by a negative sign.
Consider the region just after $y$-axis, notice that the graph decreases rather than increases.