If a and b are roots of x^2 + px + q = 0 and c and d are the roots of x^2 + px - r = 0 then (a-c)(a-d) is equal to _______?

(answer in terms of p and q and r)

Dear Shaurya,

x 2 ? p x ? q ? 0
? ?? ? ?p ..........................(1)
?? ? ?q ..........................(2)
x 2 ? p x ? r ? 0
? ?? ? p ..........................(3)
?? ? r ..........................(4)
Now
?? ?? ??? ?? ?
= ? 2 ? ?? ?? ?? ???
= ? 2 ? p? ? r using (3) & (4)
= q + r ? (? is root of x2 + px - q = 0
? ? 2 ? p? ? q ? 0
? ? 2 ? p? ? q )

Cracking IIT just got more exciting,It s not just all about getting assistance from IITians, alongside Target Achievement and Rewards play an important role. ASKIITIANS has it all for you, wherein you get assistance only from IITians for your preparation and win by answering queries in the discussion forums. 

http://www.askiitians.com/packages/packages.aspx

So start the brain storming…. become a leader with Elite Expert League ASKIITIANS

Thanks

Aman Bansal

Askiitian Expert