Answer:
<h2>Outer Electric Field is 11250 N/C.</h2><h2>Inner Electric Field is -10000 N/C.</h2>
Step-by-step explanation:
First of all, we need to read carefully and analyse the problem. As you can see, is an electrical subject, and it's given surface charge densities and radius.
So, to calculate electric fields, we need to find the proper equation to do so: 
; as you can see, first we need to find the charges.
We can find all charges using the surface charge densities, because it has the next relation: 
; which indicates that charge density is the amount of charge per area. But, there's a problem, we don't have areas, so we have to calculate them first with this relation: 
; which gives us the surface of a sphere.
The inner surface: 
The outer surface: 
Now we can calculate the charges,
Inner charge: 
Outer charge: 
Then, we are able to calculate both fields:
Inner field: 
Outer field: 
The directions that field have is opposite each other, the inner one has an inside direction, and the outer electric field has an outside direction.
Answer:
A. 5(7+4k) = 35+ 20k
This is the same as 5(4k+7)
20k+35 is equal to 35+20k
<h3>
Answer: Choice B</h3>
With matrix subtraction, you simply subtract the corresponding values.
I like to think of it as if you had 2 buses. Each bus is a rectangle array of seats. Each seat would be a box where there's a number inside. Each seat is also labeled in a way so you can find it very quickly (eg: "seat C1" for row C, 1st seat on the very left). The rule is that you can only subtract values that are in the same seat between the two buses.
So in this case, we subtract the first upper left corner values 14 and 15 to get 14-15 = -1. The only answer that has this is choice B. So we can stop here if needed.
If we kept going then the other values would be...
row1,column2: P-R = -33-16 = -49
row1,column3: P-R = 28-(-24) = 52
row2,column1: P-R = 42-25 = 17
row2,column2: P-R = 35-(-30) = 65
row2,column3: P-R = -19-36 = -55
The values in bold correspond to the proper values shown in choice B.
As you can probably guess by now, matrix addition and subtraction is only possible if the two matrices are the same size (same number of rows, same number of columns). The matrices don't have to be square.
Answer:
Step-by-step explanation:
For this problem, it says that the company not only shipped packages, but also bought a number of stamps. From the equation 6.70+0.50x, it's fairly easy to say that 6.70 is the packages,
What's not so easy is figuring out whether or not 0.50 is the stamps, or x is. However, there's an easy way to figure it out!
From this one, we would have to use "common sense" (not my words, someone elses). Using "common sense", we have to think, can someone buy 0.50 of a stamp?
Technically yes... But would someone buy 0.5 of a stamp? Not really.
So we can safetly assume that x is the "stamp", and 0.50 is <em>the cost of the stamp</em>.
Hope this helps!
