urbanderivative
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 7
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Questions Asked

urbanderivative:
Group Title
radial solution to delta u + 4u = 0 in the ball b ={x, y, z} in R^3 : r = sqrt(x^2+y^2+z^2).
I know v'' + 4v = 0 but I dont know how to g…
 updated 3 months ago
 No Medals Yet
Mathematics

urbanderivative:
Group Title
radial solution to delta u + 4u = 0 in the ball b ={x, y, z} in R^3 : r = sqrt(x^2+y^2+z^2).
I know v'' + 4v = 0 but I dont know how to g…
 updated 3 months ago
 No Medals Yet
Mathematics

urbanderivative:
Group Title
Define the set E ={ 1/n : n is a natural #} contained in [0,1]. Prove that the function
f(x) = {1, when x exists in E
0, othe…
 updated 7 months ago
 2 replies
 No Medals Yet
Mathematics

urbanderivative:
Group Title
find the subsequential limits for sn = sin(npi/4)
 updated 8 months ago
 2 replies
 No Medals Yet
Mathematics

urbanderivative:
Group Title
Use mathematical induction to show
1/2 + 1/4 + ... 1/(2^n) = 1  1/(2^(n+1))
 updated 8 months ago
 11 replies
 1 Medal
Mathematics

urbanderivative:
Group Title
y''  4y' + 3y= 5e^t
find a particular solution Yp to the nonhomogenous equation
…
 updated 10 months ago
 No Medals Yet
Mathematics

urbanderivative:
Group Title
Ordinary Differential Equations, repeated roots.
 updated 10 months ago
 1 reply
 No Medals Yet
Mathematics

urbanderivative:
Group Title
xy''+y'=4 y(1)=1 y'(1)=8 x>0
find y' and y solutions for the IVP
 updated 10 months ago
 3 replies
 1 Medal
Mathematics

urbanderivative:
Group Title
x(t) = c_1e^{3 t} + c_2e^{3 t}.
where c_1,\,c_2 are arbitrary constants.
…
 updated 10 months ago
 No Medals Yet
Mathematics

urbanderivative:
Group Title
A tank initially contains 60 liters of fresh water. Water enters the tank at a rate of 6 liters per minute
with a salt concentration of 4 …
 updated 11 months ago
 No Medals Yet
Mathematics

urbanderivative:
Group Title
A tank initially contains 120 liters of water with 50 grams of salt.
The tank is rinsed with fresh water flowing in at a rate of 7 liters …
 updated 11 months ago
 No Medals Yet
Mathematics

urbanderivative:
Group Title
A bacteria culture is known to growth at a rate proportional to the amount present.
There are 30 strands of bacteria after 1 hour(s) in th…
 updated 11 months ago
 No Medals Yet
Mathematics

urbanderivative:
Group Title
A radioactive material decays at a rate proportional to the amount present.
Initially there are 100 milligrams of the material present and …
 updated 11 months ago
 12 replies
 1 Medal
Mathematics

urbanderivative:
Group Title
y' = 3y  2e(^7t)
find the potential function (phi) [do not include the arbitrary constant c] to the differential equation
…
 updated 11 months ago
 No Medals Yet
Mathematics

urbanderivative:
Group Title
Find the integral ( from 0 to 2): qdq / (8q +5) im trying to use u substitution.
 updated one year ago
 3 replies
 2 Medals
Mathematics

urbanderivative:
Group Title
The halflife of radioactive cobalt is 5.27 years. If 100 grams of radioactive cobalt is present now, answer the following:
find an expon…
 updated one year ago
 No Medals Yet
Mathematics

urbanderivative:
Group Title
4^.2x = 2/3
 updated one year ago
 3 replies
 1 Medal
Mathematics

urbanderivative:
Group Title
A culture of bacteria obeys the law of exponential growth. If 500 bacteria are present initially and there are 800 after 1 hour.
fin an …
 updated one year ago
 1 reply
 1 Medal
Mathematics

urbanderivative:
Group Title
Size of population P P(t)=500e^(.02t)
explain to me how to do it
 updated one year ago
 6 replies
 No Medals Yet
Mathematics

urbanderivative:
Group Title
Let R be a commutative ring with identity. We will say that an ideal I of R is called "prime" is ab in I implies that either a is in I or b…
 updated one year ago
 16 replies
 1 Medal
Mathematics

urbanderivative:
Group Title
Consider the set S of matrices of the form
\left[\begin{matrix} a & b\\ 0 & c\end{matrix}\right]
with a, b, c real numbers.
…
 updated one year ago
 8 replies
 2 Medals
Mathematics

urbanderivative:
Group Title
let n be an odd integer. Assume that a is an integer such that a=2(modn) show that gcd(a,n) = 1
 updated one year ago
 6 replies
 No Medals Yet
Mathematics

urbanderivative:
Group Title
prove that R* x R is a group under the operation * defined by (a,b) * (c,d) = (ac, bc + d)
 updated one year ago
 61 replies
 4 Medals
Mathematics

urbanderivative:
Group Title
Show that R={( a 0 / b c)}  a,b, c are elements of Z} i a ring with identity.
a 0 / b c is the matrix with a 0 the first row and b c the…
 updated one year ago
 25 replies
 2 Medals
Mathematics

urbanderivative:
Group Title
Suppose I and J are ideals in a ring R and let f: R > R/I X R/J be the function defined by f(a)=(a+I, a+J).
a) Prove that f is a homomor…
 updated one year ago
 7 replies
 1 Medal
Mathematics

urbanderivative:
Group Title
if (m,n) = 1 in Z, prove that (m) intersect with (n) is the ideal (mn)
 updated one year ago
 3 replies
 No Medals Yet
Mathematics

urbanderivative:
Group Title
list the distnct principal ideals in each ring :
a Z5
b Z9
…
 updated one year ago
 No Medals Yet
Mathematics

urbanderivative:
Group Title
I cannot solve the second part
Two narrow slits are illuminated by a laser with a wavelength of 550 nm. The interference pattern on a scr…
 updated one year ago
 1 reply
 3 Medals
Mathematics

urbanderivative:
Group Title
show that q /(x^22) is not isomorphic to q /(x^23)
 updated one year ago
 52 replies
 2 Medals
Mathematics

urbanderivative:
Group Title
A certain capacitor in a circuit has a capacitive reactance of 36.8 Ω when the frequency is 136 Hz. What capacitive reactance does the capa…
 updated one year ago
 3 replies
 No Medals Yet
Mathematics
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