MATH 251
MIDTERM EXAMINATION I
February 20, 2002
PENN STATE UNIVERSITY
There are 5 multiple choice and 7 partial credit problems in this examination. Each multiple
choice problem has 5 choices. Circle the correct answer. Each multiple choice problem is
worth 5 points.
The use of calculators during the examination is forbidden.
Check your examination booklet carefully.
There should be 12 problems on 10 pages.
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MIDTERM EXAMINATION I
PAGE 2
1. (5 points) Which of the following is TRUE?
a)
y
0
=
t
y
is a Frst order linear di±erential equation
b) sin
t y
00
+ (1

t
2
)
y
0
+ cos
t y
= 0
is a second order linear di±erential equation
c)
y
00
+ (
y
0
)
3
+
y
= 0
is a nonlinear di±erential equation of order 3
d)
y
00
+
y
0
+
y
=
t
is a second order homogeneous di±erential equation
e)
∂y
∂t
+
ty
= 0
is an ordinary di±erential equation
2. (5 points) Let
y
(
t
) be the solution of the initial value problem
dy
dx
=
y
3

y
y
(0) =
9
10
.
Then lim
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 Spring '08
 CHEZHONGYUAN
 Math, Differential Equations, Equations, Partial Differential Equations, Boundary value problem, Midterm Examination

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