Cho 6 số thỏa mãn: xa+yb=c ,xb+yc=a, xc+ya=b; abc khác 0

Tính P= [tex]$\frac{a^{2}}{bc}$ + $\frac{b^{2}}{ca}$ + $\frac{c^{2}}{ab}$[/tex]

Respuesta :

Answer:

Step-by-step explanation:

xa+yb=c

xb+yc=a

xc+ya=b

add

x(a+b+c)+y(a+b+c)=a+b+c

x+y=1 ... (1)

xac+ybc=c²

xab+yac=a²

xbc+yab=b²

add

x(ab+bc+ca)+y(ab+bc+ca)=a²+b²+c²

[tex]x+y=\frac{a^2+b^2+c^2}{ab+bc+ca} \\\frac{a^2+b^2+c^2}{ab+bc+ca} =1\\a^2+b^2+c^2=ab+bc+ca\\a^2+b^2+c^2-ab-bc-ca=0\\a^3+b^3+c^3-3abc=(a+b+c)(a^2+b^2+c^2-ab-bc-ca)=(a+b+c)(0)=0\\a^3+b^3+c^3=3abc\\\frac{a^3}{abc} +\frac{b^3}{abc} +\frac{c^3}{abc} =3\\\frac{a^2}{bc} +\frac{b^2}{ca} +\frac{c^2}{ab} =3[/tex]