C/m rằng:
\(\frac{\left(x-a\right)\left(x-c\right)}{\left(c-a\right)\left(c-b\right)}+\frac{\left(x-a\right)\left(x-c\right)}{\left(b-a\right)\left(b-c\right)}+\frac{\left(x-b\right)\left(x-c\right)}{\left(a-b\right)\left(a-c\right)}=1\)với a, b, c khác nhau