Question

Is every straight line the graph of a function?

Answer 1

No, every straight line is not a graph of a function.

Nearly all linear equations are functions because they pass the vertical line test.

`y=100`
`y=x`
`y=4x`
`y=10x+4`
`y=-2x-9`

The exceptions are relations that fail the vertical line test.

x = some constant

`x = 0`
`x=99`
`x=-3`