Deterimine the value of t20 in the followinf arithmetic sequence:
1, -2, -5, -8, .........
To find the value of t20 in an arithmetic sequence, we need to first identify the common difference (d) between the terms.
In this case, we can see that each term is decreasing by 3. So, the common difference (d) is equal to -3.
Next, we can use the formula for the nth term of an arithmetic sequence, which is given by:
tn = a + (n-1)d
Here, tn represents the nth term, a represents the first term, n represents the position of the term we want to find, and d represents the common difference.
Given that a = 1 (first term) and d = -3 (common difference), we can substitute the values into the formula to find the value of t20:
t20 = 1 + (20-1)(-3)
t20 = 1 + 19(-3)
t20 = 1 - 57
t20 = -56
Therefore, the value of t20 in the arithmetic sequence 1, -2, -5, -8, ... is -56.