Step-by-step explanation:

The simplest method is "brute force". Calculate each term and add them up.
∑ = 3(1) + 3(2) + 3(3) + 3(4) + 3(5)
∑ = 3 + 6 + 9 + 12 + 15
∑ = 45

∑ = (2×1)² + (2×2)² + (2×3)² + (2×4)²
∑ = 4 + 16 + 36 + 64
∑ = 120

∑ = (2×3−10) + (2×4−10) + (2×5−10) + (2×6−10)
∑ = -4 + -2 + 0 + 2
∑ = -4
4. 1 + 1/4 + 1/16 + 1/64 + 1/256
This is a geometric sequence where the first term is 1 and the common ratio is 1/4. The nth term is:
a = 1 (1/4)ⁿ⁻¹
So the series is:

5. -5 + -1 + 3 + 7 + 11
This is an arithmetic sequence where the first term is -5 and the common difference is 4. The nth term is:
a = -5 + 4(n−1)
a = -5 + 4n − 4
a = 4n − 9
So the series is:

-7-5+3=1
-12+3=1
-9≠1. As a result, this is False. Hope it help!
The smallest county is 129 square miles large.
Step-by-step explanation:
Let,
Smallest county = x
Largest county = y
According to given statement;
The largest county in the state of Texas is 6064 square miles larger than the smallest county in the same state.
y = x+6064 Eqn 1
The size of the largest county is 48 times the size of the smallest county plus one square mile.
y = 48x+1 Eqn 2
As Eqn 1 and Eqn 2 are both equal to y, therefore,
Eqn 1 = Eqn 2

Dividing both sides by 47

The smallest county is 129 square miles large.
Keywords: linear equation, substitution method
Learn more about substitution method at:
#LearnwithBrainly
The first one is the answe<span>r.</span>
Answer:
28
Step-by-step explanation:
16−(−12)
=16−(−12)
=16+12
=28
____________________________________________________________
28 is your answer
(Hope it helps)