Question

Find the maximum sum of the A.P.40+38+36+34+32+....

Answer 1

Answer:

an=a+(n-1)d

0=40+(n-1)(-2)

0=40-2n+2

n=21

s21=21÷2 (80+(20)(-20))

=21÷2 (80-400)

21÷2×380

sum=3990

Answer 2

Answer:

40+38+36+34.......

In this A.P we know that

a(first term)=40

d(a2-a1)=-2

while n (number of terms) is not given.

also we dont know what is the value of last term

if we would have been knew those terms we can easily calculate Sum of ap

Formula is n/2(2a+(n-1)d)

SUM OF N TERMS = n/2(2×40)+(n-1)(-2)

we don know n or any other through which we can calculate exact sum of ap

so the max sum of ap upto n terms will be infinity