Draw the graph of the function YOU DONT HAVE TO DRAW THE GRA
y = f(x) = 5/x
between
x = 1/2
and
x = 4.
Find the slope of the line between the following points.
(a)
x = 3 and x = 3.1
(b)
x = 3 and x = 3.01
(c)
x = 3 and x = 3.001
(d) Now use algebra to find a simplified rational expression for the slope of the line between
(3, f(3))
and
(3 + h, f(3 + h)),
(h ? 0).
(Simplify your answer completely.)______________
(e) What do these slopes tend toward as h is made closer and closer to 0?_________
Solution
f(x) = 5/x
 a f(3) = 5/3
 f(3.1) = 5/3.1
 The slope from (3, 5/3) to (3.1, 5/3.1) =
 
 (5/3.1 - 5/3)/(3.1-3) =
 5(1/3.1 - 1/3)/(3.1-3)
 5(3 - 3.1)/(3.1(3))/(3.1-3) =
 -5/(3.1(3)) = -5/9.3 = -50/93  -0.537634408602151
 
 b)f(3.01) = 5/3.01
 The slope from (3, 5/3) to (3.01, 5/3.01) =
 
 (5/3.01 - 5/3)/(3.01-3) =
 5(1/3.01 - 1/3)/(3.01-3)
 5(3 - 3.01)/(3.01(3))/(3.01-3) =
 -5/(3.01(3)) = -5/9.03 = -500/903  -0.553709856035437
 
 c)f(3.001) = 5/3.001
 The slope from (3, 5/3) to (3.001, 5/3.001) =
 
 (5/3.001 - 5/3)/(3.001-3) =
 5(1/3.001 - 1/3)/(3.001-3)
 5(3 - 3.001)/(3.001(3))/(3.001-3) =
 -5/(3.001(3)) = -5/9.003 = -5000/9003  -0.555370432078196
d) f(3+h) = 5/(3+h)
The slope from (3, 5/3) to (3+h,5/(3+h) ) =
(5/(3+h) - 5/3)/(3+h - 3) =
5(1/(3+h) - 1/3)/h =
5(3 - (3+h))/((3+h)3)/h =
5(-h)/(9+3h)/h =
-5/(9+3h)
e) As h goes to 0, 9 + 3h goes to 9, and -5/(9+3h) goes to -5/9 -.555555555555556


