Question

x, y e Z+,
(2x + y + 1) (x -y – 4) = 23
x + y = ?
​

Answer 1

(2x + y + 1)(x - y - 4) = 23

23 - простое число ⇒ 23 = 23 * 1

$\left \{ {{2x+y+1=23} \atop {x-y-4=1}} \right.\\\\\left \{ {{y=x-4-1} \atop {2x+y+1=23=2}} \right.\\\\\left \{ {{y=x-5} \atop {2x+x-5+1=23}} \right.\\\\\left \{ {{y=x-5} \atop {3x=27}} \right.\\\\\left \{ {{x=9} \atop {y=9-5=4}} \right.\\\\x+y=9+4=13\\\\Otvet:13$