Please help asap!

The original function is

f(x)  = 2x  - 1

So

f(-x)  means  that  we replace  "x"  with "-x"  in the original function

So

f(-x)  = 2(-x)  - 1  =   -2x - 1

Here are both graphs....:  

https://www.desmos.com/calculator/ob8iw0ihx3 1

Note  the  effect of replacing "x" with "-x"    .....it just "reflects" the original graph across the y axis.....!!!