by find f(-1) do u mean x=-1? if that's the case then the problem looks like -11(-1)+2=13 OR are we solving for f??? If we are solving for F then do this:
f(−1)=(−11)(−1)+2
Step 1: Simplify both sides of the equation.
f(−1)=(−11)(−1)+2
−f=11+2
−f=(11+2)(Combine Like Terms)
−f=13
−f=13
Step 2: Divide both sides by -1.
−f/−1=13/−1
f=-13