Question

ma puteti ajuta va rog la b. va roggg mult​

Answer 1

Explicație pas cu pas:

$\dfrac{a}{b + c} = \dfrac{b}{c + a} = \dfrac{c}{a + b}$

proporții derivate:

$\dfrac{a}{a + b + c} = \dfrac{b}{b + c + a} = \dfrac{c}{c + a + b} \\ \implies a = b = c = k$

$A = 7 \cdot \dfrac{a + b}{b + c} + 5 \cdot \dfrac{b + c}{c + a} + 4 \cdot \dfrac{c + a}{a + b} =$

$= 7 \cdot \dfrac{2k}{2k} + 5 \cdot \dfrac{2k}{2k} + 4 \cdot \dfrac{2k}{2k}$

$= 7 + 5 + 4 = 16 = 4^{2} \in \mathbb{N}$

q.e.d.