Đáp án:
a.$ x=-15, y=-24$
b.$x=\dfrac12, y=-\dfrac73$ hoặc $x=17, y=16$
Giải thích các bước giải:
a.Ta có:
$\dfrac{2x}{y}=\dfrac54$
$\to \dfrac{2x}{5}=\dfrac{y}{4}$
$\to \dfrac{2x}{5}:2=\dfrac{y}{4}:2$
$\to \dfrac{x}{5}=\dfrac{y}{8}=\dfrac{x-y}{5-8}=\dfrac{9}{-3}=-3$
$\to x=-15, y=-24$
b.Ta có:
$\dfrac{2x-1}{3}=\dfrac{3y+7}{5}=\dfrac{4x+3y+5}{2x-23}$
$\to \dfrac{4x-2}{6}=\dfrac{3y+7}{5}=\dfrac{4x+3y+5}{2x-23}$
$\to\dfrac{4x-2+3y+7}{6+5}=\dfrac{4x+3y+5}{2x-23}$
$\to\dfrac{4x+3y+5}{11}=\dfrac{4x+3y+5}{2x-23}$
$\to 2x-23=11\to x=17$
$\to \dfrac{2\cdot 17-1}{3}=\dfrac{3y+7}{5}$
$\to y=16$
Hoặc $4x+3y+5=0$
$\to \dfrac{2x-1}{3}=\dfrac{3y+7}{5}=\dfrac{0}{2x-23}=0$
$\to x=\dfrac12, y=-\dfrac73$
