Question

show that the sum of an AP
whose first term is A the second
terms is B and the last term is
c. is qual to (a+c) (b+c-2a) by

2(b-a)​

Answer 1

first term = A

second term=B

common difference (d)= B-A

last term= C

sum of terms of a .p = n/2 {2A+ (n-1)d}

c=A+(n-1)d (as d= B-A)

n= B+C-2A/B-A

therefore sum of terms ={ B+C-2A/2(B-A)} {A+C}

= (A+C) ( B+C-2A)/2(B-A)

Hope this will help

Answer 2

plz refer to this attachment