Archive
23rd of March 2017
Mathematics
Q:

Find the value of a3 + b3 +6ab -8 when a+b =2 ?

Vikas Mahajan - CBSE - Class IX

Thursday, March 23, 2017 at 17:46:PM

A:

begin mathsize 16px style Given space straight a plus straight b space equals 2
Cubing space on space both space the space sides comma space we space get space
left parenthesis straight a plus straight b right parenthesis cubed space equals space 2 cubed space space
rightwards double arrow straight a cubed space plus space straight b cubed space plus space 3 ab left parenthesis straight a space plus space straight b right parenthesis space equals space 8
rightwards double arrow space straight a cubed space plus space straight b cubed space space plus space 3 ab left parenthesis 2 right parenthesis space equals space 8 space space space
rightwards double arrow straight a cubed space plus space straight b cubed space plus 6 ab space minus 8 space equals space 0 end style

Thursday, March 23, 2017 at 18:05:PM