Question

A function f is defined by f(x)=|x-a|+b Given that f(3)=3 and f(-1)=3. FInd the value of a and b

I am not sure if my working is correct.

When f(-1)=3
|-(1+a)|+b=3
1+a+b=3
a+b=2

When f(3)=3
|3-a|+b=3
b=a