X1 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.

y= -