Question

Помогите найти "?"
x+y=10
x*y=9
x-y= ?

Answer 1

Ответ:   -8  или  8  .

$\left\{\begin{array}{l}x+y=10\\xy=9\end{array}\right\ \ \left\{\begin{array}{l}y=10-x\\x\cdot (10-x)=9\end{array}\right\ \ \left\{\begin{array}{l}y=10-x\\x^2-10x+9=0\end{array}\right\\\\\\\left\{\begin{array}{l}y=10-x\\x_1=1\ ,\ x_2=9\end{array}\right\ \ \left\{\begin{array}{l}y_1=9\ ,\ y_2=1\\x_1=1\ ,\ x_2=9\end{array}\right\ \ \ \ (1;9)\ \ ,\ \ (9;1)$

$x_1-y_1=1-9=-8\\\\x_2-y_2=9-1=8$