You can see its rising so its slope is certainly positive. But by how much is it rising? You can observe that each unit it rises it goes 1 forward and 1 up so its slope is the ratio of 1 up and 1 forward which is just 1.

We have thusly,

$y=x+n$

Now look at where blue line intercepts y-axis, -1. That is our n.

So the blue line has the equation of,

$y=x-1$

Next the black lines. The black lines are axes so their equations are a bit different.

First let's deal with x-axis, does it have slope? Yes but it is 0. The x-axis is still, not rising nor falling. Where does x-axis intercept y-axis? At 0. So the equation would be,

$y=0x+0=0$

Now we have y-axis. Does y axis have a slope? Yes but it is $\infty$ . The y-axis rises infinitely in no run. Where does it intercept y-axis? Everywhere! So what should the equation be? What if we ask where does y-axis intercept x-axis and write its equation in terms of x. Y-axis intercepts x-axis at 0 which means its equation is,

$x=0$

That is, every point of a form $(0,a)$ lies on y-axis.

Hope this helps :)

8 0

3 years ago