$S_{n} = \frac{n}{2} (4n + 20) \\ \\S _{n - 1} = \frac{(n - 1)}{2} (4n - 4 + 20) \\ \\ S _{n - 1} = \frac{(n - 1)}{2} (4n + 16) \\ \\S _{n - 1} = \frac{(n - 1)(4n + 16)}{2} \\ \\ { \boxed{S _{n - 1} = {2 {n}^{2} + 6n - 8}}} \\$

(b).

from general equation:

$S _{n - 1} = \frac{(n - 1)}{2} (4n + 16)$

first term is 4n

common difference:

$16 = \{(n - 1) - 1 \}d \\ 16 = (n - 2)d \\ d = \frac{16}{n - 2}$

8 0

3 years ago

a section of ground measures 1.5 cubic meters and contains 0.78 gram of gold. what is the amount of gold per cubic meter? explai

I am Lyosha [343]

The answer

the amount of gold per cubic meter can be found by the ratio

0.78 g /1 .5 cubic meters = 0.52 g / cubic meter,
proof
it was said the amount of gold per cubic meter (Density)

7 0

3 years ago

How do you write a ratio as a percent

Vikentia [17]

Take the ratio
4:8
Convert it to a fraction
4/8
Divide
.5
Multiply by 100 and add a % sign
50%

3 0

3 years ago

Find a solution to the ineqality x > 6. A. 4 B. 11 C. 2 D. 6

Delicious77 [7]

It would be B. 11 is bigger then 6

5 0

3 years ago

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