Question

Write a function rule for the table.

f(x) = 4 – x
f(x) = –4x
f(x) = x + 4
f(x) = x – 4

Answer 1

f(x) = x - 4

Explanation:

The options are:

f(x) = 4 – x

f(x) = –4x

f(x) = x + 4

f(x) = x – 4

For f(x) = 4 – x, when x=3, f(x)=1 so it cannot be right.

For f(x) = –4x, when x=3, f(x)=-12 so it cannot be right either.

f(x) = x + 4, when x=3, f(x)=7 so it cannot be right.

The only choice left which is also the right answer is f(x) = x – 4

Answer 2

f(x) = x – 4

checking for all the functions by replacing x as 3

f(x) = 4 – x

f(3) = 4 - 3

f(3) = 1

does not match

f(x) = –4x

f(3) = -4(3)

f(3) = -12

does not match

f(x) = x + 4

f(3) = 3 + 4

f(3) = 7

does not match

f(x) = x – 4

f(3) = 3 - 4

f(3) = -1

matches