Question 62300
Age (yr)                20   30   40   50   60   70
Pulse rate (beats/min)  175  166  157  148  139  130



Write an equation in function notation for the relation.
If you were to plot this relation letting x= age and y= pulse rate, you would find that if you connected the dots they make a perfect line.
In order to write a linear function, you need a point and a slope.  We have plenty of points, let's find the slope using the slope formula: {{{highlight(m=(y2-y1)/(x2-x1))}}}, m=slope, (x1,y1) and (x2,y2) are points.
Let (x1,y1)=(20,175) and (x2,y2)=(30,166)
{{{m=(166-175)/(30-20)}}}
{{{m=-9/10}}}
{{{m=-.9}}}
Now that we have the slope and a point we can use the point slope formula.{{{highlight(y-y1=m(x-x1))}}}
m=-.9 and (x1,y1)=(20,175)
{{{y-175=-.9(x-20)}}}
{{{y-175=-.9x+18}}}
{{{y-175+175=-.9x+18+175}}}
{{{y=-.9x+193}}}
Remember, y=pulse rate and x=age, in function notation:
{{{highlight(f(x)=-.9x+193)}}}  where pulse rate is a function of age.
Happy Calculating!!!