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The sum of the first 11 terms of an arithmetic sequence is 407. What is
the first term if the last term is 67?
A. 7
B. 10
C. 14
D. 21

Sagot :

Answer:

A

Step-by-step explanation:

set 1st term is x, and public errand is d

x + (x+d) + (x+2d) + ... (x + 10d) = 407

x + 10d =67

1) = 11x + 55d= 407

2) x11 11x + 110d= 737

3) -1 = 55d = 330 d=6

so x=67 - 10d = 67-60=7

=7

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