Sum: a+b/2,a,3a-b/2,.... to 21 terms
these are in ap.
common difference(d)=a-b/2
first term(A)=a+b/2
number of terms(n)=21
sum=n/2[2a+(n-1)d]
21/2[2*(a+b/2)+(21-1)(a-b)/2]
sum=21/2[11a-9b]
Sum: a+b/2,a,3a-b/2,.... to 21 terms
these are in ap.
common difference(d)=a-b/2
first term(A)=a+b/2
number of terms(n)=21
sum=n/2[2a+(n-1)d]
21/2[2*(a+b/2)+(21-1)(a-b)/2]
sum=21/2[11a-9b]