# Finding Y-Intercept

• May 27th 2008, 06:34 PM
HTS
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?
• May 27th 2008, 07:20 PM
elizsimca
Quote:

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.
• May 27th 2008, 07:48 PM
Reckoner
Quote:

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)\$

• May 27th 2008, 07:52 PM
elizsimca
Quote:

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)\$