Answer:
105 = a
Step-by-step explanation:
L = a + (n-1)*d
n = 65
d = -2
L = u21 = 65
65 = a + (21 - 1)*(-2) Divide by - 2
65 = a + 20*-2 Multiply 20 times - 2
65 = a - 40 Add 40 to both sides
65+40 = a Combine
105 = a
The value of the first term is 105
The nth term of an arithmetic sequence is gotten by using the formula:
= a + (n - 1)d
The value of the 21st term which has been given in the question is 65 and the common difference is -2. This will be:
a + (n - 1)d = 65
a + (21 - 1)d = 65
a + 20d = 65
Since d, common difference = -2
a + 20d = 65
a + 20(-2) = 65
a - 40 = 65
a = 60 + 45
a = 105
In conclusion, the value of the first term is 105
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