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 = 
<h3>
Answers:</h3>
Variation Constant: k = 7/6
y = 245/6 when x = 7 and z = 5
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Explanation:
"y varies jointly as x and z" means that y = kxz
We have (x,y,z) = (4,14,3) as one triple, so,
y = kxz
14 = k*4*3
14 = 12k
12k = 14
k = 14/12
k = 7/6 is the variation constant
The equation goes from y = kxz to y = (7/6)xz
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Plug in x = 7 and z = 5 to find y
y = (7/6)xz
y = (7/6)*7*5
y = (7/6)*(7/1)*(5/1)
y = (7*7*5)/(6*1*1)
y = 245/6
Answer:
524,288
Step-by-step explanation:
Hope this helps!
Answer:
x=5 and y=-2
Step-by-step explanation:
3x+5y=5
-(7x+5y=25)
-4x=-20
x=5
plug 5 into one of the equations. 3(5)+5y=5
y= -2