Answer:
a) 5151 b) 249001 c)24651 d)43561
Explanation:
a) a1=1 a2=2
d=a2-a1= 2-1=1
Define the quantity of the terms of this sequence
an=a1+d(n-1)
101= 1+ 1(n-1)
n=101
Sn= (a1+an)/2*n=( (1+101)/2)*101=51*101=5151
b) a1=1 a2=3
d=a2-a1=3-1=2
an=a1+d(n-1)
997= 1+ 2(n-1)
498= n-1
n=499
Sn= (a1+an)/2*n= (1+997)/2*499= 249001
c) a1=4 a2=9
d=a2-a1=9-4=5
an=a1+d(n-1)
494=4+5(n-1)
n=99
Sn= (a1+an)/2*n=( 4+494) /2*99= 498/2*99= 249*99= 24651
d) a1=881, a2=872
d=a2-a1= 872-881=-9
an= a1+d(n-1)
8=881-9*(n-1)
9(n-1)= 873
n=98
Sn= (a1+an)/2*n= (881+8)/2*98= 889*49= 43561