Answer: 

<u>Step-by-step explanation:</u>
a) This is an arithmetic sequence where 3 is added to the previous term.
48 + 3 = 51
51 + 3 = 54
54 + 3 = 57
The recursive formula for this sequence is:
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b) This is a geometric sequence where 2.5 is multiplied to the previous term.
100(2.5) = 250
250 (2.5) = 625
625(2.5) = 1562.5
The recursive formula for this sequence is: 
The ratio 21:14 when divided by 7 on each side, is the smallest ratio that has the same value as 21:14. this becomes 3:2
then multiply both sides by a few different numbers on both sides each ,
for example, 3:2 is the same as
6:4 (3:2 times 2)
9:6 (3:2 times 3)
12:8 (3:2 times 4)
15:10 (3:2 times 5) and so on
the ratio of the right number I
divided by the left on all of them is 1.5
so,
14/10 equals 1.4 (nope)
8/4 equals 2 (nope)
9/6 equals 1.5 (yay)
12/21 equals 0.57 (Lol)
So your answer is 9:6
x = k/2 + 11/2
Step-by-step explanation:
hope this helped :)
I think 55 because you would multiply 11×5