Question

решить систему уравнений 2х+y=7 х^2-y=1

Answer 1

Сложим:
2x + y = 7 
x^2 - y = 1 
-----------------
x^2 + 2x = 8 
x^2 + 2x - 8 = 0 
D = 4 + 4*8 = 4 + 32 = 36 = 6^2
x1 = ( - 2 + 6)/2 = 4/2 = 2 
x2 = ( -  2 - 6)/2 = - 8/2 = - 4 

x1 = 2
y1= 7 - 2x = 7 - 2*2 = 7 - 4 = 3 

x2 = - 4
y2 = 7 - 2*(-4) = 7 + 8 = 15 

Ответ:
( - 4; 15) ; ( 2; 3)