Question

bhaio aur baheno koi to solve kar do ​

Answer 1

1(I) given that a3=2 and d=1

then A3= a+(n-1)d

2=a+(3-1)1

2=a=2*1

a= 2-2 = 0

A8 = a+7d

0+7(1)

=7

a8=7

an= a+(n-1)d

an= 0+(n-1)1

an = 0+n-1

an = n-1

(ii) A1=a=8 and A2= 6 then d= 6-8 = -2

A8= a+7d

= 8+7(-2)

=8-14

= -6

a8= -6

an= a+(n-1)d

an= 8+(n-1)-2

an= 8-2n+2

an=10-2n (divide whole throughout by 2)

an=5-n

(iii) A10=6 and a12=15

a+9d =6 and a+11d = 15 (subtract both)

9d-11d = 6-15

-2d = -9

d=4.5

substitute d in a+9d = 6

then a + 9(4.5) =6

a+ 40.5=6

a=6-40.5

a = - 34.5

a8 = a +7d

a8 = -34.5 +7(4.5)

a8 = -3

an= a+(n-1)d

an= -34.5 +(n-1)(4.5)

an = -34.5 +4.5n -4.5

an= -39+4.5n

an =4.5n -39