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Answer = -7
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Known
a = 13
U2 = 6
U3 = -1
U4 = -8
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Question
d = ..?
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Way to do
#since it gives a lot of number, i will just pick one of the nth term, ill choose U2
Un = a + (n-1)d
U2 = 13 + (2-1)d
6 = 13 + d
6 - 13 = d
d = -7
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Note
• The formula of arithmetic sequence
Un = a + (n-1)d
n = nth term
a = first term
d = common difference
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