The answer is the last one 300
Answer:
c=80
Step-by-step explanation:
Based on my reading the critical damping occurs when the discriminant of the quadratic characteristic equation is 0.
So let's see that characteristic equation:
20r^2+cr+80=0
The discriminant can be found by calculating b^2-4aC of ar^2+br+C=0.
a=20
b=c
C=80
c^2-4(20)(80)
We want this to be 0.
c^2-4(20)(80)=0
Simplify:
c^2-6400=0
Add 6400 on both sides:
c^2=6400
Take square root of both sides:
c=80 or c=-80
Based on further reading damping equations in form
ay′′+by′+Cy=0
should have positive coefficients with b also having the possibility of being zero.
<h3>Answer is -2</h3>
I hope it is helpful for you ....
Answer:
First mechanic worked for 10 hours and second mechanic worked for 15 hours.
Step-by-step explanation:
Let first mechanic worked for X hours and second mechanic worked for Y hours .
Now, according to the question , they worked for a total of 25 hours .
Thus ,
X + Y = 25.
Y = 25 - X -(1)
Also, first mechanic is charging $ 95 per hour and second mechanic is charging $115 per hour .
Thus, total money charged by them will be 95X + 115Y .
Which is given to be $2675 in the question.
Thus 95X + 115Y = 2675. -(2)
Putting equation 1 in equation 2 we get ,
95X + 2875 - 115X = 2675
20X = 200
X = 10 hours.
Thus , Y = 25 - X = 15 hours.
Thus first mechanic worked for 10 hours and second mechanic worked for 15 hours.
