19/20 x (1/10 + 4/5 x (1 + y) – 3/20 = y tìm y

Đáp án:

$\frac{95}{32}$

Giải thích các bước giải:

$\frac{19}{20}$ . [$\frac{1}{10}$ + $\frac{4}{5}$ . (1+y) -$\frac{3}{20}$ ] = y

⇔ $\frac{19}{20}$ . [$\frac{1}{10}$ + $\frac{4}{5}$ + $\frac{4}{5}$.y -$\frac{3}{20}$ ] = y

⇔ $\frac{19}{20}$ . ($\frac{3}{4}$ + $\frac{4}{5}$.y ) = y

⇔ $\frac{19}{20}$ . $\frac{3}{4}$ + $\frac{19}{20}$ . $\frac{4}{5}$y = y

⇔ $\frac{57}{80}$ + $\frac{19}{25}$y – y = 0

⇔ y($\frac{19}{25}$ -1) = – $\frac{57}{80}$ 

⇔ – $\frac{6}{25}$y = – $\frac{57}{80}$ 

⇔ y = – $\frac{57}{80}$ : – $\frac{6}{25}$

⇒ y = $\frac{95}{32}$