Question

Решите пожалуйста 1 и 5 задание!!)))
Срочно

Answer 1

$1)left { {{x^{2}-y^{2}=-5} atop {y+x=1}} right.\\left { {{(x+y)(x-y)=-5} atop {x+y=1}} right.\\+left { {{x-y=-5} atop {x+y=1}} right. \\------\2x=-4\\x=-2\\y=1-x=1-(-2)=1+2=3\\Otvet:boxed{(-2;3)}$

$5)left { {{x^{2}+3xy=18 } atop {x-y=2}} right. \\left { {{y=x-2} atop {x^{2}+3x*(x-2)=18 }} right.\\left { {{y=x-2} atop {x^{2}+3x^{2}-6x-18=0}} right. \\left { {{y=x-2} atop {4x^{2}-6x-18=0 }} right.\\left { {{y=x-2} atop {2x^{2}-3x-9=0}} right.\\2x^{2}-3x-9=0\\D=(-3)^{2}-4*2*(-9)=9+72=81=9^{2}\\x_{1} =frac{3-9}{4}=-1,5\\x_{2}=frac{3+9}{4}=3\\y_{1} =-1,5-2=-3,5\\y_{2}=3-2=1 \\Otvet:boxed{(-1,5;-3,5),(3;1)}$