# pre algebra

posted by
**Anonymous**
.

write an equation for the line through the given points or through the given point with the given slope

(5,7),(6,8)

(1,2),(3,8)

(0,5),(-3,2)

(8,11),(6,16)

For each of them, use the standard formula

(y- y1) = [(y2-y1)/x2-x1)]*(x-x1)

In the first case, that gives you

(y-7) = (1/1)* (x-5)

y = x+2

drwls, thanks for the help. I was trying to check my sons answers. He got the first one right. When he is doing this homework he is not sure of what he is doing. I showed him this and asked if he understood the standard formula and he looked like a deer in headlights! I said to make the graph and maybe that would help. Any other help. Thanks

In the "standard formula"

[(y2-y1)/(x2-x1)]

is the slope of the line, usually called "m".

The standard formula is just is a mathematical statement that the change in y from a point (x1,y1) is equal to the slope, multiplied by the change in x measured from the same point. Some texts may use a different approach, but I find the one that I wrote easiest to remember.

Applying the same method to the second problem,

y -2 = (6/2) (x-1)

y = 2 + 3x -3

y = 3x - 1