Answer: Choice A
S9 = (9/2)*(2+26)
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The formula is
Sn = (n/2)*(a1+an)
where
Sn = sum of the first n terms (nth partial sum)
n = number of terms
a1 = first term
an = nth term
In this case,
n = 9
a1 = 2 (plug in n = 1 into the formula an = 3n-1 and simplify)
an = a9 = 26 (plug n = 9 into the formula an = 3n-1 and simplify)
So,
Sn = (n/2)*(a1+an)
S9 = (9/2)*(2+26)
will help us find the sum of the first 9 terms of this arithmetic sequence
Answer:Gcf=1.
Step-by-step explanation: The factors of 2 are: 1, 2
.
The factors of 6 are: 1, 2, 3, 6
.
The factors of 15 are: 1, 3, 5, 15.
Answer: 231
<u>Explanation:</u>
Liwen Celina
5x 6x
5x - 21 =
6x
5x - 21 = 4x
<u>-4x +21</u> <u>-4x +21 </u>
x = 21
Liwen: 5x = 5(21) = 105
Celina: 6x = 6(21) =<u> 126</u>
Total: 231
Answer:

Step-by-step explanation:
The time constant of the isotope is:


The decay of the isotope is described by the following model:

Now, the time is cleared in the equation:


