Question 62300
This is a linear equation.  That is, as age increases, pulse rate decreases.
Use the formula for a slope and the slope-intercept formula to solve.
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The x's are the ages.
The y's are the pulse rates.
So, match-up the ages and pulse rates to form a list of coordinate pairs:
(20, 175) 
(30, 166) 
(40, 157)
(50, 148)
(60, 139)
(70, 130)
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Slope=m=(y1-y2)/(x1-x2)[use the formula for the slope of a line]
m=(175-166)/(20-30) [plug-in the values and solve for the slope of the line]
m=9/-10=-9/10
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y=mx+b [use the slope-intercept formula]
175=(-9/10)(20)+b [plug-in the values and solve for b]
175=118+b
175+18=b
193=b [plug the slope and y-intercept (b) back into the equation}
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y=mx+b
y=(-9/10)x+193 [the equation of the line]
or f(x)=(-9/10)x+193 [function notation]