Question

What is the range of f(x) = 3x + 9?

{y | y < 9}
{y | y > 9}
{y | y > 3}
{y | y < 3}

Answer 1

Range(f) = all real numbers, (-∞, ∞).

Reason: for any real y, x = (y − 9)/3 gives f(x) = y, so every real y occurs. None of the four given options is correct.