Question

[$x2-2y2=-14 x+y=1$

Answer 1

  x^2 - 2y^2 = - 14

  x  + y =1 ==> x = 1 - y 
x1= 1 - y1 ==> x1 = 1 - 3 ==> x1 = - 2
x2= 1- y2 ==> x2 = 1 - (-5) ==> x2 = 1 + 5 ==> x2 = 6

( 1 - y ) ^2 - 2y^2 + 14 = 0

1 - 2y + y^2 - 2y^2 + 14 = 0

- y^2 - 2Y + 15 = 0(-1)

y^2 + 2y - 15 = 0

delta = 2^2 - 4.1.(-15)= 4 + 60 = 64

y = - 2 +/- V64 = - 2 + /- 8 ==>x1= - 2 + 8 =>x1 = 3 ; x2= - 2 - 8 ==> x2 = - 5
              2.1               2                      2                                 2