Đáp án+ Giải thích các bước giải:
$1, x + y = - 95 → y = - 95 - x$
$thay$ $vào$ $xy = 2016$ $ta$ $có:$
$x(-95 - x) = 2016$
$→ - x² - 95x = 2016$
$→ x² + 95x + 2016 = 0$
$→ (x² + 63x) + (32x + 2016) = 0$
$→ x(x + 63) + 32(x + 63) = 0$
$→ (x + 32)(x + 63) = 0$
$→\left[ \begin{array}{l}x + 32 = 0\\x+ 62 = 0\end{array} \right.→\left[ \begin{array}{l}x=-32\\x=-63\end{array} \right.$
$→\left[ \begin{array}{l}y = - 63\\y = -32\end{array} \right.$
$Vậy$ $(x ; y) = (- 32 ; - 63) ; (- 63 ; - 32)$
$2, x + y = 25 → x = 25 - y$
$thay$ $vào$ $\frac{2x}{3} = \frac{5y}{4}$ $ta có:$
$\frac{2(25-y)}{3}=\frac{5y}{4}$
$→ 8(25 - y)= 15y$
$→ 200 - 8y = 15y$
$→ 23y = 200$ $→ y = \frac{200}{23}$
$→ x = 25 - \frac{200}{23} = \frac{375}{23}$
$Vậy$ $(x ;y) = (\frac{375}{23} ; \frac{200}{23})$
