The sum of the first four terms of the sequence is 22.
In this question,
The formula of sum of linear sequence is

The sum of the first ten terms of a linear sequence is 145
⇒ 
⇒ 145 = 5 (2a+9d)
⇒ 
⇒ 29 = 2a + 9d ------- (1)
The sum of the next ten term is 445, so the sum of first twenty terms is
⇒ 145 + 445
⇒ 
⇒ 590 = 10 (2a + 19d)
⇒ 
⇒ 59 = 2a + 19d -------- (2)
Now subtract (2) from (1),
⇒ 30 = 10d
⇒ d = 
⇒ d = 3
Substitute d in (1), we get
⇒ 29 = 2a + 9(3)
⇒ 29 = 2a + 27
⇒ 29 - 27 = 2a
⇒ 2 = 2a
⇒ a = 
⇒ a = 1
Thus, sum of first four terms is
⇒ 
⇒ 
⇒ S₄ = 2(2+9)
⇒ S₄ = 2(11)
⇒ S₄ = 22.
Hence we can conclude that the sum of the first four terms of the sequence is 22.
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240 days is 4 times the half-life, which means that a sample of 1000 mg will decay to

after 240 days.
I believe the answer is 267
If each is worth $25 and it costs $10 then he is making $15 profit.
4000/15 is 266.6666667
So you would need 267
Answer:
is true your answer hhhhhhhhgghdhxhhchdjfjf
Answer:
Perpendicular
Skew
Parallel
Step-by-step explanation:
First one : the lines intersect and they form right angles
The second one : they don't intersect and appear on separate planes
The last : they are both sides of a rectangle on the same plane