Page 226 - aljaber

RQS@ @pþÝn¾aì@pbÉibnn¾a ()
a2011 a4 = a3 + d = a1 + 3d .

an = a1 + (n − 1)d
2, 9, 16, 23, 30, …

9 − 2 = 16 − 9 = 23 − 16 = 30 − 23 = 7

.d = 7 a1 = 2
. a2011 = a1 + 2010d = 2 + 2010 × 7 = 14072

a,b,c

b −a = c −b

2b = a + c

b = a +c
2

(arithmetic mean)

.

3k + 1, k, − 3 ()
.k