Question

1) Factorise:
9a^2 + 4b^2 +16c^2 +12ab -16bc - 24ca.
2) if a+b+c = 9 and ab + bc + ca = 26 , a^2+b^2+c^2

Answer 1

I hope this is correct

Answer 2

Answer:

9a² + 4b² + 16c² + 12ab - 16bc - 24ca

=> ( - 3a )² + ( - 2b )² + ( 4 c )² + 2[ ( -3a × -2b ) + ( -2b × 4c ) + ( 4c × - 3a ) ]

We know, a² + b² + c² + 2( ab + bc + ca ) = ( a + b + c )²

Hence,

=> [ ( -3a ) + ( -2b ) + ( 4c ) ]²

=> ( -3a - 2b + 4c )²

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