Answer:
28
Step-by-step explanation:
10-38=28
$&#:÷&#&;#&$;'ebsjdkeowkdbs;#&$;'fbxjrbxjr
Answer: 59.5
Step-by-step explanation:
U(t) = 5.1t^2 − 1.7t
U'(t)=2*5.1t-1.7
U'(t)=10.2t-1.7
U'(6)=10.2(6)-1.7
U'(6)=61.2-1.7
U'(6)=59.5
Answer:
15 days
Step-by-step explanation:
Let x be the number of days needed for B to complete the job. Then x-5 is the number of days needed for A to complete the job.
In 1 day,
- A completes
of all work; - B completes
of all work.
Hence, in 1 day both A and B complete
of all work. A and B working together can do a work in 6 days. Then
![6\cdot \left(\dfrac{1}{x-5}+\dfrac{1}{x}\right)=1.](https://tex.z-dn.net/?f=6%5Ccdot%20%5Cleft%28%5Cdfrac%7B1%7D%7Bx-5%7D%2B%5Cdfrac%7B1%7D%7Bx%7D%5Cright%29%3D1.)
Solve this equation:
![\dfrac{6x+6x-30}{x(x-5)}=1,\\ \\12x-30=x^2-5x,\\ \\x^2-17x+30=0,\\ \\D=(-17)^2-4\cdot 30=289-120=169=13^2,\\ \\x_{1,2}=\dfrac{17\pm 13}{2}=2,\ 15.](https://tex.z-dn.net/?f=%5Cdfrac%7B6x%2B6x-30%7D%7Bx%28x-5%29%7D%3D1%2C%5C%5C%20%5C%5C12x-30%3Dx%5E2-5x%2C%5C%5C%20%5C%5Cx%5E2-17x%2B30%3D0%2C%5C%5C%20%5C%5CD%3D%28-17%29%5E2-4%5Ccdot%2030%3D289-120%3D169%3D13%5E2%2C%5C%5C%20%5C%5Cx_%7B1%2C2%7D%3D%5Cdfrac%7B17%5Cpm%2013%7D%7B2%7D%3D2%2C%5C%2015.)
If
then
that is impossible. So, B needs 15 days to complete the work alone.
For this case we have the following system of two equations with two unknowns:
![-2x + y + 6 = 0\\2x + y-8 = 0](https://tex.z-dn.net/?f=-2x%20%2B%20y%20%2B%206%20%3D%200%5C%5C2x%20%2B%20y-8%20%3D%200)
Adding both equations we have to eliminate the variable "x":
![y + y + 6-8 = 0](https://tex.z-dn.net/?f=y%20%2B%20y%20%2B%206-8%20%3D%200)
Adding common terms, keeping in mind that different signs are subtracted and the sign of the major is placed:
![2y-2 = 0\\2y = 2](https://tex.z-dn.net/?f=2y-2%20%3D%200%5C%5C2y%20%3D%202)
Answer:
![2y = 2](https://tex.z-dn.net/?f=2y%20%3D%202)
Option A