bt tết

C

chonhoi110

Bài 1:
$M=\dfrac{bc}{(a-b)(a-c)}+\dfrac{ac}{(b-a)(b-c) }+\dfrac{ab}{(c-b)(c-a)}$

$=\dfrac{bc(b-c)-ac(a-c)+ab(a-b)}{(a-b)(a-c)(b-c)}$

$=\dfrac{bc(b-c)-ac(a-b+b-c)+ab(a-b)}{(a-b)(a-c)(b-c)}$

$=\dfrac{c(b-c)(b-a)+a(a-b)(b-c)}{(a-b)(a-c)(b-c)}$

$=\dfrac{(b-c)(b-a)(c-a)}{(a-b)(a-c)(b-c)}$

$=1$
 
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