The 5th term of an AP is 13 and the 1st term is -3. Find the 6th term and the sum of the first
12 terms.
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a6 = 17
Sum = 228
Step-by-step explanation:
a5 = 13
a = -3
a5 = a + 4d
13 = -3 + 4d
13 + 3 = 4d
16 = 4d
16/4 = d
d = 4
a6 = a + 5d
a6 = -3 + 5(4)
a6 = -3 + 20
a6 = 17
a = -3
a2 = a + d = -3 + 4 = 1
a3 = a2 + d = 1 + 4 = 5
a4 = a3 + d = 5 + 4 = 9
a5 = a3 + d = 9 + 4 = 13
a6 = 17
a7 = a6 + d = 17 + 4 = 21
a8 = a7 + d = 21 + 4 = 25
a9 = a8 + d = 25 + 4 = 29
a10 = a9 + d = 29 + 4 = 33
a11 = a10 + d = 33 + 4 = 37
a12 = a11 + d = 37 + 4 = 41
Adding all 12 terms,
-3 + 1 + 5 + 9 + 13 + 17 + 21 + 25 + 29 + 33 + 37 + 41
= 228
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