@selgofetish hmm it's been ages since i learnt this but i think set up two equations, one where the first two parts of the function are equal and x = 2 and a second one where the last two parts of the function are equal and x = 5 and solve them as simultaneous equations to get a and b?
@onlydaylights i don't really know anything about makeup so take this rec with a grain of salt but i use the bare minerals barepro liquid foundation and i really like it!! i'm not sure if you can get it at sephora though, i got mine from mecca