Page 248 - aljaber

RSU@ @pþÝn¾aì@pbÉibnn¾a .4 ()
:( )
.an = 2011 d = 3 a1 = −8

an = a1 + (n − 1)d
2011 = −8 + (n − 1) × 3

2022 = 3n

.n = 2022 = 674
3

:( ) ()
()
.a10 = a1r 9 = 6 × (12)9 = 2 × 3 × 218 × 39 = 219 × 310
()
d = −2 a1 = 36 :( )
3 .an = −30

an = a1 + (n − 1)d

−30 = 36 + (n − 1)− 2 
3

−66 − 2 = − 2 n
33

− 200 = − 2 n
33
.n = 100

.ar 3 = 324 ar = 144 :( )

ar 3 = 324
ar 144
r 2 = 2.25