Marco wants to set up 12 small wind turbines with 3 blades each. If 4 wind turbine blades cost $79.74, how much will all the bla
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The formula to find any term of an an arithmetic sequence is given by
=
=(n-1)d,
where we have first term
=8,
and d which is the common difference , and n is the term we need to find (in our case is 20)
the difference d=3, as you see each number is the previous minus 3
for S20=8+(20-1)*(-3)=8+(19)*(-3)=8-57=-49
S20=-49, this the 20th term
where we have first term
and d which is the common difference , and n is the term we need to find (in our case is 20)
the difference d=3, as you see each number is the previous minus 3
for S20=8+(20-1)*(-3)=8+(19)*(-3)=8-57=-49
S20=-49, this the 20th term