Question 1136299
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Let the first term be a and the common difference be r.  Then<br>
v2 = ar
v3 = ar^2
v4 = ar^3<br>
Then from the given information,<br>
{{{6 = ar^3-ar^2 = r(ar^2-ar) = 5r}}}
{{{r = 6/5}}}<br>
Then this with the given information gives us<br>
{{{ar^2-ar = a(36/25-6/5) = a(6/25) = 5}}}
{{{a = 125/6}}}<br>
Then the first four terms are<br>
125/6, 25, 30, 36<br>
Their sum is 671/6 or 111 5/6.