Question

if a+b+c= 9 and ab+bc+ca=26,find a square +b square + c square= ?

Answer 1

9×9 -2(26)=81-52
=29 is the correct answer.

Answer 2

Hi ,

a + b + c = 9 -- -- ( 1 )

ab + bc + ca = 26------( 2 )

Multiply each term with 2 in equation

( 2 ) , we get

2ab + 2bc + 2ca = 52 ---( 3 )

Now do the square of equation ( 1 ) ,

( a + b + c )² = 9²

a² + b² + c ² + 2ab + 2bc + 2ca = 81

a² + b² + c² + 52 = 81

a² + b² + c² = 81 - 52

= 29

I hope this helps you.

:)