Archive
23rd of March 2017
Mathematics
Q:

If a2 + b2 + c2 = 30 and a+b+c = 10, then find the value of ab+BC+CA?

Vikas Mahajan - CBSE - Class IX

Thursday, March 23, 2017 at 16:30:PM

A:

begin mathsize 16px style straight a squared plus straight b squared plus straight c squared equals 30 space and space straight a plus straight b plus straight c equals 10
left parenthesis straight a plus straight b plus straight c right parenthesis squared equals straight a squared plus straight b squared plus straight c squared plus 2 ab plus 2 bc plus 2 ac
rightwards double arrow left parenthesis 30 right parenthesis squared equals 30 plus 2 left parenthesis ab plus bc plus ac right parenthesis
rightwards double arrow 900 equals 30 plus 2 left parenthesis ab plus bc plus ac right parenthesis
rightwards double arrow 870 equals 2 left parenthesis ab plus bc plus ac right parenthesis
rightwards double arrow 445 equals ab plus bc plus ac end style

Thursday, March 23, 2017 at 16:59:PM