## anonymous one year ago The points 1,r and −3,1 lie on a line with slope −1 Find the missing coordinate r.

1. MrNood

do youknow how to work out the slope of a line betwee 2 points?

2. anonymous

No can you teach me?

3. MrNood

|dw:1443312124889:dw| the slope is the steepness of the line it is calculated from the 2 points like this: $slope = \frac{ y _{2}-y _{1} }{ x _{2}-x _{1} }$

4. MrNood

in your question you have the 2 points (1,r) & (-3,1) and you know th eslope is -1 so put the numbers that you know into the equation you then need to arrange it to work out r

5. MrNood

|dw:1443312430012:dw| use the equatin and the numbers - you can then work out r