1.

The first term of an arithmetic sequence is 7 and the sixth term is 22. Find(a) The common difference;(b) The twelfth term;(c) The sum of the first 100 terms.

Answer»

ANSWER:

(a) 3

(b) 40

(C) 15,550

Step-by-step EXPLANATION:

(a) Given a = 7

term-6 i.e. a+5d=22

put a=7 in a+5d

i.e. a+7d=22

7+5d=22

5d=15

d=3.

(b) term - 12 = a+11d

i.e. 7+11(3)

= 7+33

=40.

(c) S sub 100 = 100/2 [2(7)+ {100-1}3]

= 50 [14+{99(3)}

=50 {14+297}

=50 {311}

=15,550


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