Răspuns:
f(x) = a(x+√2 -2)
Explicație pas cu pas:
f: R ---> R ; f(x) = ax+b
f(1)+f(2) = f(1+√2)
f(1) = a+b
f(2) = 2a+b
f(1+√2) = a(1+√2) +b
f(1)+f(2) = a+b+2a+b = 3a+2b
f(1)+f(2) = f(1+√2) =>
3a +2b = a(1+√2) +b <=>
3a-a-a√2 +b = 0 <=>
a(2-√2) = -b => b = a(√2-2)
f(x) = ax + a(√2-2) => f(x) = a(x+√2 -2)
