Respuesta :
Answer:
-36.
Step-by-step explanation:
First term a1 = 21.
Common difference d = 18 - 21 = -3 (15-18 = -3)
nth term an = a1 + (n - 1)d
So 20th term = 21 + (20-1) -3
= 21 - 3 * 19
= 21 - 57
= -36.
The 20th term of the arithmetic sequence will be -36.
The nth teem of an arithmetic sequence is calculated by using the formula: a + (n - 1) d.
The 20th term will be:
= a + (n - 1) d.
= a + (20 - 1)d
= a + 19d
where,
a = first term = 21
d = common difference = 2nd term - 1st term = 18 - 21 = -3
Therefore, 20th term will be:
= a + 19d
= 21 + 19(-3)
= 21 - 57
= -36
Therefore, the 20th term is -36
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