the first three terms of an arithmetic sequence are 20, 16 and ,12 wich element is -60?
A. 18
B. 19
C. 20
D. 21
pa answer po please salamat❤
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the first three terms of an arithmetic sequence are 20, 16 and ,12 wich element is -60?
A. 18
B. 19
C. 20
D. 21
pa answer po please salamat❤
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Answer:
D. 21
Step-by-step explanation:
[tex]a_{n}[/tex] = -60
[tex]a_{1}[/tex] = 20
d = -4
n = ?
[tex]a_{n}[/tex] = [tex]a_{1}[/tex] + (n - 1) d
-60 = 20 + (n - 1) (-4)
-60 - 20 = -4n + 4
-80 = -4n + 4
-80 - 4 = -4n
-84 = -4n
divide both sides by -4
21 = n