The points (-4, r) and (4, -1) lie on a line with slope -1. find the missing coordinate r.

7

Step-by-step explanation:

The formula for slope is where is the slope and are points on the line.

We can use that formula but I like to line my points up vertically and subtract and then put 2nd difference over 1st difference.

(-4,r)

minus

(4,-1)

--------

-8  r-(-1)

So we have:

Multiply both sides by -8:

Subtract 1 on both sides:

.

Let's check:

(-4,7)

minus

(4,-1)

-------

-8 8

So the slope is 8/-8=-1 which is what we wanted.

So the value for r being 7 has been checked and verified.

add an image !

step-by-step explanation:

30 miles

step-by-step explanation:

we know that 60 seconds equals 1 minute and 60 minutes 1 hour

44 ft       60 sec     60 min     158400   ft

  *   *   =

1 sec       1 min       1 hour         hour

we know that there are 5280 ft per mile

158400   ft       1 mile         30 miles

  *   =

1   hour               5280 ft     1 hour

so in 1 hour   it can travel 30 miles