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In an arithmetic sequence a_7-2a_4=1, a_3=0. Find the common difference

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Final answer:

To find the common difference, we utilized the properties of an arithmetic sequence and the given conditions. By expressing the terms a_7 and a_4 in terms of the first term and the common difference, and substituting a_3's value, we deduced that the common difference is 1/2.

Step-by-step explanation:

To find the common difference in an arithmetic sequence given a_7 - 2a_4 = 1 and a_3 = 0, we need to use the definition of an arithmetic sequence, which has the form: a_n = a_1 + (n-1)d, where a_n is the nth term, a_1 is the first term, d is the common difference, and n is the term number.

First, we express a_7 and a_4 in terms of a_1 and d:

  • a_7 = a_1 + 6d
  • a_4 = a_1 + 3d

Substituting these into the given equation:

(a_1 + 6d) - 2(a_1 + 3d) = 1

Expanding and simplifying gives:

a_1 + 6d - 2a_1 - 6d = 1

-a_1 = 1

We also know that a_3 = 0, so:

a_3 = a_1 + 2d = 0

Substituting a_1 = -1 into the expression for a_3, we get:

-1 + 2d = 0

Therefore, the common difference d is:

d = 1/2

User Charles Beattie
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