26 tháng 8 2016 lúc 9:27
Cho 5 số thực khác nhau a,b,c,d,x.Chứng minh :
\(\frac{b+c+d}{\left(b-a\right)\left(c-a\right)\left(d-a\right)\left(x-a\right)}+\frac{a+c+d}{\left(a-b\right)\left(c-b\right)\left(d-b\right)\left(x-b\right)}+\frac{a+b+d}{\left(a-c\right)\left(b-c\right)\left(d-c\right)\left(x-c\right)}+\)
\(\frac{a+b+c}{\left(a-d\right)\left(b-d\right)\left(c-d\right)\left(x-d\right)}=\frac{a+b+c+d-x}{\left(a-x\right)\left(b-x\right)\left(c-x\right)\left(d-x\right)}\)
