Question

Решите систему уравнений:
х+у=1
х^2-y^2=9

Answer 1

$\left \{ {x+y=1 } \atop {x^2-y^2=9}} \right.$

$\left \{ {{{x+y = 1}} \atop { x^2 = y^2+9}} \right.$

$\left \{ {{{x+y = 1}} \atop { (x-y) (x+y) = 9}} \right.$

$\left \{ {{{y = 1-x}} \atop { x^2-y^2 = 9}} \right.$

$\left \{ {{x = 5 } \atop { y = -4}} \right.$

График внизу если надо

Answer 2

Х^2 - y^2 = 9
( x - y )•( x + y ) = 9
X + y = 1
X - y = 9
2x = 10
X = 5
5 + y = 1
y = - 4
Проверка
5 + ( - 4 ) = 1
1 = 1
5^2 - ( - 4 )^2 = 9
25 - 16 = 9
9 = 9
ОТВЕТ ( 5 ; - 4 )