Question

Решите систему уравнений {x-y=7 {x*y=-10

Answer 1

X = Y + 7 
Y*( Y + 7) = - 10 
Y^2 + 7Y + 10 = 0
D = 49 - 40 = 9
√ D = 3 
Y1 = ( - 7 + 3 ) : 2 = - 2 
Y2 = ( - 10) : 2 = - 5 
X = Y + 7 
X1 = - 2 + 7 = 5 
X2 = - 5 + 7 = 2 
Ответ ( 5 ; - 2 ) ; ( 2 ; - 5 ) 

Answer 2

$left { {{x-y=7} atop {x*y=-10}} right. \ x=7+y \ y(7+y)=-10 \ y^{2} +7y+10=0 \ D=49-40=9 \ sqrt{D} =3 \ y _{1} = frac{-7+3}{2} = frac{-4}{2} =-2 \ y _{2} = frac{-7-3}{2} = frac{-10}{2} =-5 \ x_{1} =7-2=5 \ x_{2} =7-5=2 \ left { {{x=5} atop {y=-2}} right. left { {{x=2} atop {y=-5}} right.$