825 - 625i
Hope it’s right
Best luck with your studying
B. (k+10f)(k-5f) you can tell in 2 ways. 1. if the second sign is neg then the signs in the factors are going to be one neg and one positive so that knocks out C and D. Then you look at the second term and since the 5 is positive then the 10 has to be positive so you end up with a positive 5kf.
The second way is to FOIL them out. When you check B you get

combine your like terms and you have your original expression of

Hope that helps
Answer:

Step-by-step explanation:
<u>Ratios
</u>
We are given the following relations:
![a=\sqrt{7}+\sqrt{c}\qquad \qquad[1]](https://tex.z-dn.net/?f=a%3D%5Csqrt%7B7%7D%2B%5Csqrt%7Bc%7D%5Cqquad%20%5Cqquad%5B1%5D)
![b=\sqrt{63}+\sqrt{d}\qquad \qquad[2]](https://tex.z-dn.net/?f=b%3D%5Csqrt%7B63%7D%2B%5Csqrt%7Bd%7D%5Cqquad%20%5Cqquad%5B2%5D)
![\displaystyle \frac{c}{d}=\frac{1}{9} \qquad \qquad [3]](https://tex.z-dn.net/?f=%5Cdisplaystyle%20%5Cfrac%7Bc%7D%7Bd%7D%3D%5Cfrac%7B1%7D%7B9%7D%20%5Cqquad%20%5Cqquad%20%5B3%5D)
From [3]:

Replacing into [2]:

We can express 63=9*7:

Taking the square root of 9:

Factoring:

Find the ration a:b:

Simplifying:

Answer:
-1
Step-by-step explanation: