Question

[Ngô Bao Chau]

Số nguyên y thõa mãn (y+5)/(7-y)=2/-5 là ?

Answer 1

[Akai Haruma]

Lời giải:

$\frac{y+5}{7-y}=\frac{2}{-5}$

$\Rightarrow \frac{y+5}{y-7}=\frac{2}{5}$

$\Rightarrow 5(y+5)=2(y-7)$

$\Rightarrow 5y+25=2y-14$
$\Rightarrow 5y-2y=-14-25$

$\Rightarrow 3y=-39$
$\Rightarrow y=-39:3=-13$