A2 Edexcel C3 Solomon help

Hello, does anyone know the general method to answer answer question 4 part a?
Thanks
https://b3755649dbd1afe3db91a899c3b9837b22326254.googledrive.com/host/0B1ZiqBksUHNYMG14YWtobVJUUms/for-Edexcel/Solomon%20H%20QP%20-%20C3%20Edexcel.pdf

Mod f(x) takes positive values and returns the same positive values - it takes negative values and multiplies them by -1, in effect.

(The real definition is mod(f(x)) = max(f(x), -f(x))).

So just sketch the graph and reflect any negative regions in the x axis.

Whoops sorry I meant part b
Thanks though

You've got two sets of co-ordinates given so you can form simultaneous equations.