Question

if a+b+c=12 and a×a+b×b+c×c=64 find ab +bc+ac

Answer 1

here is ur answer mate.....

Answer 2

Given,
a + b + c = 12
a² + b² + c² = 64
ab + bc + ca = ?

===========================

a + b + c = 12

square on both sides,

(a + b + c)² = (12)²
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By Formula,
$(a + b + c)^2 = a^2 + b^2 + c^2 + 2(ab + bc + ca)$
=================

(a + b + c)² = (12)²

a² + b² + c² + 2(ab + bc + ca) = 144


Putting the given values,

64 + 2(ab + bc  + ca)  = 144

2(ab + bc + ca) = 144 - 64 

2(ab + bc + ca) = 80

ab + bc + ca = 80/2 

ab + bc + ca = 40 



i hope this will help you


-by ABHAY