Question

expand , using suitable identities:
(3a - 7b -c)²​

Answer 1

Step-by-step explanation:

( x + y + z )²

= x² + y² + z² + 2xy + 2yz + 2zx

Now ,

( a - b - c )²

=[ a² + ( - b )² + ( -c )² ]²

=a²+(-b)²+(-c)²+2a(-b)+2(-b)(-c)+2(-c)a

= a² + b² + c² - 2ab + 2bc - 2ca

(3a)² + (7b)² + c² - 2*3a*7b + 2*7b*c - 2*c*3a

9a² + 49b² + c² - 42ab + 14bc - 6ac ans.

thank you