We're given f(x-1) = x+1
then f(x) = x+2
Remember f(x) means you're replacing whatever's in f(x) into the x value. Try putting the first one back into the equation
f(x-1) = (x-1) +2 = x-1 +2 = x+1

We're given f(x-1) = x+1
then f(x) = x+2
Remember f(x) means you're replacing whatever's in f(x) into the x value. Try putting the first one back into the equation
f(x-1) = (x-1) +2 = x-1 +2 = x+1