Answer:

Step-by-step explanation:
In order to write the series using the summation notation, first we need to find the nth term of the sequence formed. The sequence generated by the series is an arithmetic sequence as shown;
4, 8, 12, 16, 20...80
The nth term of an arithmetic sequence is expressed as Tn = a +(n-1)d
a is the first term = 4
d is the common difference = 21-8 = 8-4 = 4
n is the number of terms
On substituting, Tn = 4+(n-1)4
Tn = 4+4n-4
Tn = 4n
The nth term of the series is 4n.
Since the last term is 80, L = 4n
80 = 4n
n = 80/4
n = 20
This shows that the total number of terms in the sequence is 20
According to the series given 4 + 8 + 12 + 16 + 20+ . . . + 80
, we are to take the sum of the first 20terms of the sequence. Using summation notation;
4 + 8 + 12 + 16 + 20+ . . . + 80 = 
Answer: Parallel: y=-2/7x-2 1/7 Perpendicular: y=7/2x+13
Step-by-step explanation:
2x+7y=14
Subtract 2x from both sides.
7y=-2x+14
Divide both sides by 7 to isolate y.
y=-2/7x+2
Parallel:
Plug in x and y with same slope as the original.
-1=-2/7(-4)+b
Solve for b:
-1=8/7+b
-2 1/7=b
y=-2/7x-2 1/7
Perpendicular:
Plug in x and y with the negative inverse of the original slope.
-1=7/2(-4)+b
Solve for b.
-1=-28/2+b
-1=-14+b
13=b
y=7/2x+13
Answer:

Step-by-step explanation:
To find the inverse of a function, we must substitute in y for f(x), swap the locations of y and x, and then solve for y

Answer:
x=-7
Step-by-step explanation:
-30=5(x+1)
6-1(x+1)
x=-1-6
=-7
It's a complementary angle, so just solve for x and subtract the CBD from 90,
First, we have to solve for x.
2x + 14 + x + 7 = 90
Combine like terms
3x + 21 = 90
Balance, subtract 21 from each side.
3x = 69
Divide 3 from each side
x = 23.
So know that we know x is 23, we can go about it 2 ways, subtracting the other angle with 90 or just substituting the variable, I'd just substitute the variable for it so just do 23 + 7. That equals 30, angle ABC = 30.