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National
Easy
Sequences
10–12
For
u
n
=
4
n
−
3
u_n = 4n - 3
u
n
=
4
n
−
3
, what is the sum of the first
20
20
20
terms?
Sendo
u
n
=
4
n
−
3
u_n = 4n - 3
u
n
=
4
n
−
3
, qual é a soma dos primeiros
20
20
20
termos?
Answer options
A.
810
810
810
B.
780
780
780
C.
740
740
740
D.
1560
1560
1560
Check Answer
Solution
Step 1 of 3
1.
The sequence is arithmetic with
u
1
=
1
u_1 = 1
u
1
=
1
and
u
20
=
4
×
20
−
3
=
77
u_{20} = 4 \times 20 - 3 = 77
u
20
=
4
×
20
−
3
=
77
.
Next step
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