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

(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

Jose's car can drive 12 miles on each gallon of gas. How many gallons will he need to drive 3,298 miles?✱

masya89 [10]

Answer:

274.84 gallons.

Step-by-step explanation:

Divide 3,298 by 12

3298/12 =274.84

6 0

3 years ago

What's 6/7 written as a fraction with a denominator of 42? A. 36/42 b. 7/42 c. 42/42 d. 6/42

7nadin3 [17]

Pls mark Brainliest.

Answer:

A. 36/42

Step-by-step explanation:

What do you multiply 7 by to get 42?

6. That is what the denominator was multiplied by, and so, the equivalent fraction must have a numerator that is 6 times larger than the original.

6 is the numerator so the numerator of the equivalent fraction with denominator 42 must be 36 since 6 * 6 = 36/

A. 36/42

4 0

3 years ago