Question

хелп ми плиз !!!!!!!!!!!

Answer 1

$=a left (1-frac{1}{b+c}right ) + b left (1-frac{1}{a+c}right ) + c left (1-frac{1}{b+a}right ) = a left ( frac {1}{a+b} + frac{1}{a+c} right) +b left ( frac {1}{a+b} + frac{1}{b+c} right) + c left ( frac {1}{b+c} + frac{1}{a+c} right) = frac {a}{a+b} + frac {a}{a+c} + frac {b}{a+b} + frac {b}{b+c} + frac {c}{b+c} + frac {c}{a+c} = frac {a+b}{a+b} + frac {a+c}{a+c} + frac {b+c}{b+c} =3$