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January 26, 2015

January 26, 2015

Posted by **shyam** on Sunday, June 23, 2013 at 1:55am.

- maths -
**MathMate**, Sunday, June 23, 2013 at 6:23amAssume the equation has three roots a,b and c:

then

(x-a)(x-b)(x-c)=0

x³-(a+b+c)x²+(ab+bc+ca)x-abc=0

which means

(a+b+c)=-3 (negative of coeff.of x²)

(ab+bc+ca)=-7 (coeff. of x)

Hence

a²+b²+c²

=(a+b+c)²-2(ab+bc+ca)

=3²-2(-7)

=9-(-14)

=23

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