Question

find the sum of all terms of an A.P. -11,-8,-5..........…....49​

Answer 1

Answer:

$\huge{ \underline{ \underline{ \pink{ \green{ \blue{ \orange{ \pink{ \purple{ \red{a}{n} }{s} }{w} }{e} }{r} }{} }{} }{} }{} }{}$

$given$

a = -11

d = 3

an = 49

n = 49

Sn = n/2(2a+n-1)d

Sn = 49 /2 ( -22+144)

---> 49/2*122

So, by calculation....

2989 is the answer

Answer 2

Step-by-step explanation:

tn=49 a=-11 d=3

tn=a+(n-1)d

49=-11+(n-1)3

49= -11+3n-3

49=3n - 14

49+14=3n

63=3n

n=21

Sn=n/2(2a+(n-1)d)

=21/2(2×-11+(21-1)3)

=21/2(-22+20×3)

=21/2(-22+60)

=21/2(38)

=21×19

=399