Question

What are the domain and range of f(x) = 4x – 8?

domain: {x | x is a real number}; range: {y | y > –8}
domain: {x | x is a real number}; range: {y | y > 8}
domain: {x | x > 4}; range: {y | y > –8}
domain: {x | x > –4}; range: {y | y > 8}

Answer 1

f(x)=4x−8 is a linear function with nonzero slope, so its domain and range are all real numbers.

Domain: {x | x is a real number}
Range: {y | y is a real number}

(Equivalently, for any y you can solve x = (y+8)/4, so every real y is attained. None of the four given choices is correct.)