Question 633025
The declared value (in $) is {{{y=3800}}} for {{{x=0}}}.
After {{{x}}} years, the declared value has decreased by ${{{400x}}} to
{{{y=3800-400x}}} or in a more conventional linear equation in slope-intercept form
{{{highlight(y=-400x+3800)}}}
 
The slope intercept form of a linear equation looks like
{{{y=mx+b}}} ,
with a number {{{m}}} called the slope, multiplied to the variable {{{x}}},
and a number {{{b}}} called the y-intercept,
added to that product to yield {{{y}}}.
 
In this case the slope is {{{highlight(m=-400)}}}.
When the slope is negative, as in this case, we know that {{{y}}} decreases as {{{x}}} increases.
 
The number {{{m}}} is called the slope because it measures how fast {{{y}}} increases or decreases for an increase of one unit in {{{x}}}, increasing for positive slopes, and decreasing for negative slopes.
For {{{x=0}}} , {{{y=b}}}, and if we add {{{1}}} to the {{{x}}},
we find that for {{{x=1}}} , {{{y=m+b}}} has increased by {{{m}}}