Flag 10 grade maths> hi, can someone pls give a detailed , ste...
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hi,
can someone pls give a detailed , step by step answer for the given question ??
  1. show that the sum of an a.p whose first term is a, second term is b, and the last term is c is equal to-- (a+c) * (b+c-2a) / 2(b-a )

DAN BROWN , 8 Years ago
Grade 10
anser 3 Answers
Vijay Mukati

Last Activity: 8 Years ago

Dear Student,

As the sum of n terms of an AP whose, first term is a an last terms is l is given by:

S = (n/2)(a + l)

We have, first term = a, second term = b and last term = c
using a, b, and c find the number of terms, as we know that,
c = a + (n-1)(b-a) from here find thevalue of n and just replace in above formula to calculate the sum of terms in an AP.

Best of Luck!
Vijay

DAN BROWN

Last Activity: 8 Years ago

hello sir,
i tried doing what you asked, but am still not getting it. pls help. 
( instead of writing, if you culd send a pic it would help me understand better.)
 
regards,
dan brown ( i do not wish to reveal my name )
 

Vijay Mukati

Last Activity: 8 Years ago

on simplifying, c = a + (n-1)(b-a) we get,

n = (c + b – 2a)/(b-a)

Now this value of n in S = n/2*(a + c)
we get, S = (a + c)*(c + b -2a)/2(b-a)

I hope the steps are clear now.

Thanks. Vijay

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