How do you write the equation of the horizontal line passing through (1,9)?

he equation of any horizontal line is

y = .. a number

The x-value has no effect on the equation or on the line at all, as long as y-value stays the same.

In this case the line passes though the point (−8,9)

which tells us that the y-value we want is 9.

Therefore the equation is y=9

first option

a function is a relation in which an input is paired with exactly one output.

so, let's find the right answer.

in our first option, our inputs are january, february, and march. the outputs are 30, 28, and 25. each input has it's own output. this is correct!

our second option we know is incorrect, because ms. valverade has two outputs, dogs and cats. this is not a function.

our third option is incorrect as well. the yellow square has two ouputs, the square and the triangle.

lastly, in our fourth option, we see the number 7 two times with a different output. therefore, this is not a function.

remember: each input must be paired with only one output!