# Find the equation of the straight line joining each of the following pairs of points (a) (0, 0) and (1,-1)

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To find the equation of a line, you need to have the slope of the line and a point on the line.

The slope is found using the slope formula:

`m={y_2-y_1}/{x_2-x_1}`

`={-1-0}/{1-0}`

`={-1}/{1}`

`=-1`

Now sub in the point and slope into the equation y=mx+b to get:

`y=mx+b`

`-1=-1(1)+b`

`-1=-1+b` move -1 to left side

`-1+1=b`

`0=b`

**This means the equation of the line is `y=-x` .**

Slope m= y2-y1/x2-x1

-1-0/1-0

-1/1

=-1

equatio of line: y=mx+c

-1=-1+c

c=0

y=-x

this the equation.