slope intercept form

Question

The population of the Capitol Hall neighborhood has been growing steadily since 1985. In 1991, the population was 52600 people. In 1994, it was 55900 people. Find an equation in the form
y
=
m
x
+
b
,
y=mx+b, where
x
x is the number of years past 1985 and
y
y is the population of Capitol Hall.

Answer 1

How do you discover the slope?

Slope is defined as (difference in Y's) / (difference in X's)

So, (difference in Y's) means "subtract 1991 population from 1994 population"

(difference in X's) means "subtract 1991 from 1994"

Divide the two, to get "m", the slope.

 

Now substitute that value for m into y = mx + b, and substitute the 1991 population for "y", and substitute "years since 1985" from 1991 for "x". Solve for b.