Giải thích các bước giải:
Bài 9 :
$T$a có :
$\dfrac{6}{35} = \dfrac{2}{7} × \dfrac{3}{5} = \dfrac{3}{7} × \dfrac{2}{5}$
= $\dfrac{2}{1} × \dfrac{3}{35} = \dfrac{2}{35} × \dfrac{3}{1}$
= $\dfrac{1}{1} × \dfrac{6}{35} = \dfrac{1}{5} × \dfrac{6}{7}$
= $\dfrac{1}{7} × \dfrac{6}{5} = \dfrac{1}{35} × \dfrac{6}{1}$
Bài 10 :
$T$a có :
$\dfrac{a}{b} + \dfrac{a}{c}$
= $\dfrac{ac}{bc} + \dfrac{ab}{bc}$
= $\dfrac{ac + ab}{bc}$
= $\dfrac{a(b+c)}{bc}$
= $\dfrac{(b+c)(b+c)}{bc}$
= $\dfrac{(b+c)²}{bc} = \dfrac{a²}{bc} = \dfrac{a}{b} × \dfrac{a}{c}$
$V$ậy $\dfrac{a}{b} + \dfrac{a}{c} = \dfrac{a}{b} × \dfrac{a}{c}$
$C$húc bạn học tốt !
