# Working out the intercept of the Y-Axis

1. Dec 13, 2007

### Dearster

If a gradient of -578.947 is present on a line of best fit then how can you work out the intercept of the Y-Axis when a co-ord of:

(0.00000227, 0.00100) is given?

Thank you

2. Dec 13, 2007

### arildno

Well, a line is usually given by the equation y=ax+b, and the y-intercept i.e, the value of y when x=0 is evidently y=b.

Having given coordinates (X,Y) of some point, you know that:

Y=aX+b. Determine what a and b is from this.

3. Dec 14, 2007

### HallsofIvy

Staff Emeritus
A line with slope m, passing through $(x_0,y_0)$ has equation $y= m(x-x_0)+ y_0$. Put x= 0 and you have $y= y_0- mx_0$.