a) f(x)=ax+b
Daca A(-1,-1) ∈ Gf =>f(-1)=-a+b=-1
B(2,3) ∈ Gf =>f(2)=2a+b=3
Sistem de ecuatii cu 2 necunoscute: -a+b=-1 => b=a-1
2a+b=3 | =>2a+a-1=3 => a=4/3 & b=1/3
f(x)=4/3x+1/3
b)A(0,0)=> f(0)=b=0
B(1,-3)=>f(1)=a+b=-3/cum b=0 =>a=-3 f(x)=-3x
c) -2a+b=0 /cum b=2(din pct. B)=> a=1 f(x)=x+2