Answer:
k = 30, ![y(t) = C_1e^{5t}+C_2e^{6t}](https://tex.z-dn.net/?f=y%28t%29%20%3D%20C_1e%5E%7B5t%7D%2BC_2e%5E%7B6t%7D)
Step-by-step explanation:
Since
is a solution, then it must satisfy the differential equation. So, we calculate the derivatives and replace the value in the equation. We have that
![\frac{d^2y}{dt^2} = 25 e^{5t},\frac{dy}{dt} = 5e^{5t}](https://tex.z-dn.net/?f=%5Cfrac%7Bd%5E2y%7D%7Bdt%5E2%7D%20%3D%2025%20e%5E%7B5t%7D%2C%5Cfrac%7Bdy%7D%7Bdt%7D%20%3D%205e%5E%7B5t%7D)
Then, replacing the derivatives in the equation we have:
![25e^{5t}-11(5)e^{5t}+ke^{5t}=0 e^{5t}(25-55+k) =0](https://tex.z-dn.net/?f=25e%5E%7B5t%7D-11%285%29e%5E%7B5t%7D%2Bke%5E%7B5t%7D%3D0%20e%5E%7B5t%7D%2825-55%2Bk%29%20%3D0)
Since
is a positive function, we have that
.
Now, consider a general solution
, then, by calculating the derivatives and replacing them in the equation, we get
![Ae^{rt}(r^2-11r+30)=0](https://tex.z-dn.net/?f=Ae%5E%7Brt%7D%28r%5E2-11r%2B30%29%3D0)
We already know that r=5 is a solution of the equation, then we can divide the polynomial by the factor (r-5) to the get the other solution. If we do so, we get that (r-6)=0. So the other solution is r=6.
Therefore, the general solution is
![y(t) = C_1e^{5t}+C_2e^{6t}](https://tex.z-dn.net/?f=y%28t%29%20%3D%20C_1e%5E%7B5t%7D%2BC_2e%5E%7B6t%7D)
-4m-24=-8
(add 24 to both sides)
-4m=16
(divide by -4 on both sides)
m=-4
Answer:
Step-by-step explanation:
Let the speed of Masha = s, speed of Dasha = d
- Distance = 20 km
- Time difference = 20 min = 1/3 hr
- Speed difference = 2 km/h
<u>As per above info we get following equations:</u>
- s = d + 2
- 20/s + 1/3 = 20/d
<u>Substitute s and solve for d:</u>
<u>Get rid of fraction by multiplying all terms by 3d(d + 2):</u>
- 60d + d(d + 2) = 60(d + 2)
- 60d + d² + 2d = 60d + 120
- d² + 2d = 120
- d² + 2d + 1 = 121
- (d + 1)² = 11²
- d + 1 = 11
- d = 10
<u>Find s:</u>
<u>The answer is</u>
- Masha's speed 12 km/h and Dasha's speed 10 km/h
900/18=50
On average, 50 students rode each bus
Hope this helps!