Math 1151 NAME : ___ ___ ___ ___ ___ ___ ___ ___MIDTERM 1September 15, 2015 OSU Name.# : ___ ___ ___ ___ ___ ___ __Form APage 1 of 8 Lecturer::___ ___ ___ ___ ___ ___ ___
Recitation Instructor : ___ ___ ___ ___
Recitation Time : ___ ___ ___ ___ ___ __
INSTRUCTIONS
● SHOW ALL WORK in problems 2, 3, and 4 .Incorrect answers with work shown may receive partial credit,but unsubstantiated correct answers may receive NO credit.
You don' t have to show work in problems 1 and 5.
● Give EXACT answers unless asked to do otherwise.
● Calculators are NOT permitted!PDA' s , laptops, and cell phones are prohibited.Do not have these devices out!
● The exam duration is 55 minutes.
● The exam consists of 5 problems starting on page 2 and ending on page 8.Make sure your exam is not missing any pages before you start.
PROBLEMNUMBER
SCORE
1 (20)2 (20)3 (21)4 (21)5 (18)
TOTAL (100)
MIDTERM 1Form A, Page 2
1. (20 pts)The graph of a function f is given in the figure below.
Use the graph of f to answer the questions below.
y = f ( x )
-2 -1 1 2 3 4 5 6x
-6
-4
-2
2
4
6
y
(I) (1 pt) Find the domain of f.
Domain of f = -∞, 3) ⋃ (3, +∞)
(II) (1 pt) Find the range of f.
Range of f = (-∞, +∞)
2 SOLUTIONS-MIDTERM 1- AU 15.nb
(III) Find the following values.
Note : Possible answers include + ∞ , -∞, or "does not exist".
(a) (1 pt) limx→3
f (x) = 0
(b) (1 pt) f (3) = DNE (does not exist)
(c) (1 pt) f (5) = 2
SOLUTIONS-MIDTERM 1- AU 15.nb 3
MIDTERM 1Form A, Page 3
1. ( CONTINUED)
1. ( CONTINUED)
(d) (1 pt) limx→0-
f (x) = 0
(e) (1 pt) limx→0+
f (x) = -∞
(f) (1 pt) limx→0
f (x) = DNE
(g) (1 pt) limx→-∞
f (x) = +∞
(h) (1 pt) limx→+∞
f (x) = -6
(IV) (2 pts) Find all vertical asymptotes.
x = 0
(V) (2 pts) Find all horizontal asymptotes.
y = -6
(VI) (6 pts) Determine the intervals of continuity for f .
(-∞, 0], (0, 3), (3, 5], (5, +∞)
4 SOLUTIONS-MIDTERM 1- AU 15.nb
MIDTERM 1Form A, Page 4
2. (20 pts) SHOW YOUR WORK!0-4 -3 -2 -1 0 1 2 3 4
s
The position, s (t), of an object moving along ahorizontal line (see the figure above) is given by
s (t) = t2 - 2.
(I) Mark the position of the object at the time t = 1 on the line above.
s (1) = 12 - 2 = -1
(II) Find the average velocity, vAV , of the objectduring the time interval [1, 3].
vAV =s (3) - s (1)
3 - 1=32 - 2 -12 - 2
3 - 1=82
= 4
(III) Compute the average velocity, vAV (t), of the objectduring the time interval
(a) [1, t], for t > 1;
vAV (t) =s (t) - s (1)
t - 1= t2 - 2 - (-1)
t - 1= t2 - 1
t - 1=
= (t - 1) (t + 1)t - 1
= t + 1 , t > 1
(b) [t, 1], for 0 < t < 1.
vAV (t) =s (1) - s (t)
1 - t=
-1 - t2 - 2
1 - t= 1 - t2
1 - t=
= (1 - t) (1 + t)1 - t
= 1 + t , t < 1
OR
SOLUTIONS-MIDTERM 1- AU 15.nb 5
OR
vAV (t) =s (1) - s (t)
1 - t= s (t) - s (1)
t - 1= t2 - 2 - (-1)
t - 1=
= t2 - 1t - 1
= (t - 1) (t + 1)t - 1
= t + 1, t < 1
6 SOLUTIONS-MIDTERM 1- AU 15.nb
MIDTERM 1Form A, Page 5
2. (CONTINUED)
(IV) Find the instantaneous velocity, vinst, of the object at t = 1.Justify your answer.
vinst = limt→1
vAV (t) =limt→1
(t + 1) = 1 + 1 = 2
(V) Let s (t) = t2 - 2.The graph of of the function s is given in the figure below.
s = s ( t )
1 2 3t
-2
-1
1
2
3
4
5
6
7
s
(a) Assume P is a point on the graph of s. Fill in the blank.
P = (1, s (1)) = (1, -1)
(b) Plot the point P and draw the tangent line at this pointin the figure above.
(c) Find the slope, mtan, of the tangent line in part (b). Explain.
mtan = vinst = 2
SOLUTIONS-MIDTERM 1- AU 15.nb 7
MIDTERM 1Form A, Page 6
3. (21 pts) Evaluate the limit or say that the limit does not exist .If a limit does not exist, explain why. Show your work.
You may NOT use a table of values, a graph,or L' Hospitals' s Rule to justify your answer.
Note : Possible answers include + ∞ or - ∞.
(a) (7 pts)
limx→3
x2 - 2 x - 3
x + 1 - 2=
= limx→3
x2 - 2 x - 3
x + 1 - 2
x + 1 + 2
x + 1 + 2=
= limx→3
(x - 3) (x + 1) x + 1 + 2
x + 1 - 4=
= limx→3
(x - 3) (x + 1) x + 1 + 2
x - 3=
= limx→3
(x + 1) x + 1 +2 = (3 + 1) 3 + 1 +2 =
=4 4 +2 =16
8 SOLUTIONS-MIDTERM 1- AU 15.nb
(b) (7 pts) limx→0+
x sin (ln x)
NOTE:We cannot apply the Product Law,since lim
x→0+sin (ln x) DOES NOT EXIST.
On the other hand,-1 ≤ sin (ln x) ≤ 1
and , therefore,
-x ≤ x sin (ln x) ≤ x , (since x > 0).
Since limx→0+
x = limx→0+
-x) = 0,
the inequality above implies that
limx→0+
x sin (ln x) = 0, by the Squeeze Theorem .
EXPLANATION:Since lim
x→0+ln x=-∞,
sin (ln x) oscillates between 1 and - 1 as x → 0+,and, therefore
limx→0+
sin (ln x) DOES NOT EXIST.
(c) (7 pts) limx→2-
(ln x)→ln 2>0
(x - 2)→0-= -∞
`or
Since ln x approaches ln 2 > 0,and the denominator (x - 2) approaches 0,and is negative as x → 2-, it follows that
limx→2-
ln xx - 2
= -∞
SOLUTIONS-MIDTERM 1- AU 15.nb 9
MIDTERM 1Form A, Page 7
4. (21 pts) (I) (6 pts) Determine the value of a constant b for whichthe function g is continuous at 0.Show your work. Justify your answer!
g (x) =
2 x +bx-5 if x < 0 ,
x +16x2-16
if x ≥ 0, x ≠ 4.
We have to show that limx→0
g (x) = g (0).
g (0) =0 + 16
0 - 16= -1;
limx→0-
g (x) =limx→0-
2 x + b
x - 5=0 + b
0 - 5=
-b
5
limx→0+
g (x) =limx→0+
x + 16
x2 - 16=0 + 16
0 - 16= -1
Since limx→0
g (x) has to exist in order for g to be continuous at x = 0,
it has to be true that
limx→0-
g (x) = limx→0+
g (x) = limx→0
g (x).
Therefore,
-b5
= -1, and , so b = 5.
So, if b = 5 , limx→0
g (x) = g (0),
and therefore, g is continuous at x = 0.
10 SOLUTIONS-MIDTERM 1- AU 15.nb
In the questions below the function g is given in part (I).
(II) (4 pts) Evaluate the limit. Show your work!
(a) limx→-∞
g (x) = limx→-∞
2 x + b
x - 5= lim
x→-∞
2 + bx
1 - 5x
=limx→-∞ 2 + b
x
limx→-∞ 1 - 5x
= 2;
(b) limx→+∞
g (x) = limx→+∞
x + 16
x2 - 16= lim
x→+∞
1 + 16x→1
x - 16x→∞
= 0.
OR
(a) limx→-∞
g (x) = limx→-∞
2 x + b
x - 5= 2;
(b) limx→+∞
g (x) = limx→+∞
x + 16
x2 - 16= 0.
(III) (4 pts) Determine whether g has any horizontal asymptotes. If so,write the equation (or equations) of all horizontal asymptotes.
y = 2, by part (II) (a)
y = 0, by part (II) (b)
SOLUTIONS-MIDTERM 1- AU 15.nb 11
(IV) (7 pts) Determine whether g has any vertical asymptotes. If so,write the equation (or equations) of all vertical asymptotes.Show your work. Justify your answer!
There is no vertical asymptote at x = 5, because limx→5
g (x) =5 + 16
52 -16;
there is no vertical asymptote at x = -4, because limx→-4
g (x) =-8 + b
-4 - 5.
But,
limx→4+
g (x) =limx→4+
x + 16
x2 - 16=limx→4+
(x + 16)→20
(x - 4)→0+ (x + 4)→8=
(or the numerator goes to 20, and the denominatoris positive and goes to 0, as x → 4+)
= +∞
So, the function g has only one vertical asymptote,x = 4.
MIDTERM 1Form A, Page 8
5. (18 pts) Circle True if the statement is ALWAYS true;circle False otherwise. No explanations are required.
(a)
Let f be a one - to - one function and f-1 its inverse.
If the point (2, 5) lies on the graph of f,then the point (5, 2) lies on the graph of f-1 .
True False
f (2) = 5 ⟺ f-1 (5) = 2
(b) sin-1 (π) = 0 True False
Since π > 1 , π is not in the domain of sin-1;orsin-1 (π) ≠ 0, since sin (0) = 0 ≠ π
12 SOLUTIONS-MIDTERM 1- AU 15.nb
(c)
If f and g are two functions defined on (-1, 1), and if
limx→0
g (x) = 0, then it must be true that
limx→0
[ f (x) g (x)] = 0. True False
Let f (x) = 1/x, if x ≠ 0, and f (0) = 4 and g (x) = x.Then lim
x→0g (x) = lim
x→0(x) = 0, but
limx→0
[ f (x) g (x)] = limx→0
1x x = 1≠ 0.
(d)
If f is continuous on (-1, 1),and if f (0) = 10 and lim
x→0g (x) = 2,
then limx→0
f (x)
g (x)= 5. True False
Because limx→0
f (x)
g (x)=
limx→0 f (x)
limx→0 g (x)=f (0)
2=10
2= 5
(e)
If f is continuous on [1, 3], and if
f (1) = 0 and f (3) = 4, then the equation f (x) = π
has a solution in (1, 3).
True False
Since f continuous on [1, 3], f (1) = 0 < π < 4 = f (3),by the Intermidiate Value Theorem there exists ac in (1, 3) such that f (c) = π .
(f)
Let f be a positive function with verticalasymptote x = 5. Then
limx→5
f (x) = +∞.
True False
SOLUTIONS-MIDTERM 1- AU 15.nb 13
Let f (x) = 1, if x < 5, and f (x) =1
5 - x, if x > 5.
Then limx→5+ f (x) = +∞, and therefore, x = 5 is a vertical asymptote.
So, f is a positive function with vertical asymptote x = 5 butlimx→5
f (x) ≠ +∞, since limx→5+ f (x) = +∞ ≠ lim
x→5- f (x) = 1,
which means that limx→5
f (x) does not exist.
14 SOLUTIONS-MIDTERM 1- AU 15.nb