<span>1/r + 2/1-r = 4/r^2
1-r+2r/r(1-r)=4/r^2
(1+r)/r(1-r)=4/r^2 cancle r both side
1+r/1-r=4/r
cross multiply
r+r^2=4-4r
r^2+4r+r-4=0
r^2+5r-4=0
r^2+4r+r-4=0
solve it for r factor it...
</span>
Answer:
Your friend is incorrect because if you divide 21 by 7 you will get 3 if you add 7 to 3 you get 10 therefore your friend is incorrect.
Hello!
The answer to your problem is: 
<u>Simplify both sides of the equation</u>
<u>Subtract 2/3x from both sides</u>
<u>Subtract 2 from both sides</u>
<u>Multiply both sides by 3/(-26)</u>
<u>Get your answer</u>
Hope This Helps!
Answer:
91 short stories
Step-by-step explanation:
You just add 1 + 2 + 3 + 4 + 5 + 6... all the way to 13, and then at the end of 16 months, Troy still only wrote 91 stories since he only wrote them up until 13 months, and then stopped afterwards.
Let 
be the total amount of money paid by any given set of passengers. If there are 
passengers in a car, then the driver must pay a toll of 
.
Then has first moment (equal to the mean)
![E[Y]=E[0.5X+3]=0.5E[X]+3E[1]=0.5\mu_X+3=\boxed{4.35}](https://tex.z-dn.net/?f=E%5BY%5D%3DE%5B0.5X%2B3%5D%3D0.5E%5BX%5D%2B3E%5B1%5D%3D0.5%5Cmu_X%2B3%3D%5Cboxed%7B4.35%7D)
and second moment
![E[Y^2]=E[0.25X^2+3X+9]=0.25E[X^2]+3E[X]+9E[1]=0.25E[X^2]+3\mu_X+9](https://tex.z-dn.net/?f=E%5BY%5E2%5D%3DE%5B0.25X%5E2%2B3X%2B9%5D%3D0.25E%5BX%5E2%5D%2B3E%5BX%5D%2B9E%5B1%5D%3D0.25E%5BX%5E2%5D%2B3%5Cmu_X%2B9)
Recall that the variance is the difference between the first two moments:
![\mathrm{Var}[X]=E[X^2]-E[X]^2\implies E[X^2]={\sigma^2}_X+{\mu_X}^2](https://tex.z-dn.net/?f=%5Cmathrm%7BVar%7D%5BX%5D%3DE%5BX%5E2%5D-E%5BX%5D%5E2%5Cimplies%20E%5BX%5E2%5D%3D%7B%5Csigma%5E2%7D_X%2B%7B%5Cmu_X%7D%5E2)
![\implies E[Y^2]=0.25({\sigma^2}_X+{\mu_X}^2)+3\mu_X+9\approx19.22](https://tex.z-dn.net/?f=%5Cimplies%20E%5BY%5E2%5D%3D0.25%28%7B%5Csigma%5E2%7D_X%2B%7B%5Cmu_X%7D%5E2%29%2B3%5Cmu_X%2B9%5Capprox19.22)
![\implies\mathrm{Var}[Y]=E[Y^2]-E[Y]^2=\boxed{0.3}](https://tex.z-dn.net/?f=%5Cimplies%5Cmathrm%7BVar%7D%5BY%5D%3DE%5BY%5E2%5D-E%5BY%5D%5E2%3D%5Cboxed%7B0.3%7D)
