Sagot :
f: R -> R, f(x) = ax + b;
f(1) = 8 => a + b = 8;
f(2) = 14 => 2a + b = 14 => a = 6 and b =2;
f(3) = 20 => 6*3 + 2 = 20 True;
f(4) = 26 => 4*6 + 2 = 26 True;
then, f:R -> R, f(x) = 6x + 2;
f(1) = 8 => a + b = 8;
f(2) = 14 => 2a + b = 14 => a = 6 and b =2;
f(3) = 20 => 6*3 + 2 = 20 True;
f(4) = 26 => 4*6 + 2 = 26 True;
then, f:R -> R, f(x) = 6x + 2;