Question

what is the value of 0-1+2-3+4-5+6-7______+16-17+18-19+20.​
please answer the question as fast as possible!!!!

Answer 1

Answer:10

Step-by-step explanation:(2+4+6+.......+20) - (1+3+5+.......+19)

Now, we got two A.P.s

Let the number of terms in first A.P. be n

20 = 2 + (n - 1)(4 - 2)

20 = 2 + 2n - 2

20 = 2n

2n = 20

n = 10

Let the number of terms in second A.P. be m

19 = 1 + (m - 1)(3 - 1)

19 = 1 + 2m - 2

2m - 1 = 19

2m = 20

m = 10

sum of the series

10/2(2*2+(10-1)2) - 10/2(2*1+(10-1)2)

=5(4+9*2) - 5(2+9*2)

=5(4+18) - 5(2+18)

=5*22 - 5*20

=10