# Thread: Finding Y-Intercept

1. ## Finding Y-Intercept

I've been given a problem on finding the y-intercept, and i've been given one set of points (along with the slope) to find out the y-intercept. Now, I'm not allowed to graph, and I dont know any equation on finding the y-intercept, so can anyone help out?

2. Originally Posted by HTS
I've been given a problem on finding the y-intercept, and i've been given one set of points (along with the slope) to find out the y-intercept. Now, I'm not allowed to graph, and I dont know any equation on finding the y-intercept, so can anyone help out?

It is easiest to see the intercept in the form $\displaystyle y=mx+b$ where b is the y-intercept and m is the slope.

Use the point (x,y) and the slope (m) and plug it into the equation above. Plugging in y, x, and m will only leave you with b and you can solve for the y-intercept.

It's good to know that $\displaystyle y=mx+b$ is called the "point-slope" form of a line..if my memory serves me correctly.

3. Originally Posted by elizsimca
It's good to know that $\displaystyle y=mx+b$ is called the "point-slope" form of a line..if my memory serves me correctly.
This is actually the slope-intercept form. The name makes sense when you see that the slope is $\displaystyle m$ and the y-intercept is $\displaystyle (0,\;b)$, as you pointed out.

The point-slope form uses the slope $\displaystyle m$ and a point $\displaystyle (x_0,\;y_0)$ on the line:

$\displaystyle (y - y_0) = m(x - x_0)$

However, your advice to the OP is certainly sound.

4. Originally Posted by Reckoner
This is actually the slope-intercept form. The name makes sense when you see that the slope is $\displaystyle m$ and the y-intercept is $\displaystyle (0,\;b)$, as you pointed out.

The point-slope form uses the slope $\displaystyle m$ and a point $\displaystyle (x_0,\;y_0)$ on the line:

$\displaystyle (y - y_0) = m(x - x_0)$

However, your advice to the OP is certainly sound.
AHH!! I knew it didn't sound right..hence the disclaimer at the end. I had the epiphany as I was eating my dinner and was going to come back and edit my comment..but you caught me!!