X 1 2 3 4 5 Y 1 3 5 7 9

Given the table, write an expression for the function, and describe what it does.

A) y = 2x. Y is double x.

B) y = 3x. Y is triple x.

C) y = 2x + 1. Y is twice x plus 1.

D) y = 2x - 1. Y is twice x minus 1.

Option D:

y = 2x - 1; y is twice x minus 1.

Solution:

Option A: y = 2x; y is double x

substitute x values in y = 2x, we get

For x = 1, y = 2 (1) = 2

so, y = 2x is false.

Option B: y = 3x; y is triple x

substitute x values in y = 3x, we get

For x = 1, y = 3 (1) = 3

so, y = 3x is false.

Option C: y = 2x + 1; y is twice x plus 1.

substitute x values in y = 2x + 1, we get

For x = 1, y = 2 (1) + 1 = 3

so, y = 2x + 1 is false.

Option D: y = 2x - 1; y is twice x minus 1.

substitute x values in y = 3x, we get

For x = 1, y = 2 (1) - 1 = 1

For x = 2, y = 2 (2) - 1 = 3

For x = 3, y = 2 (3) - 1 = 5

For x = 4, y = 2 (4) - 1 = 7

For x = 5, y = 2 (5) - 1 = 9

so, y = 2x - 1 is true.

Hence the expression for the table is y = 2x - 1; y is twice x minus 1.

Each value of y is double that of corresponding value of x, minus 1.