Question

хелп
1)$left { {{x-y=5} atop {xy=-4}} right. 2)left { {{x^2+y^2=29} atop {-4x^2+y^2=9}} right.$

Answer 1

$displaystylemathtt{left{{{x-y=5}atop{xy=-4}}rightleft{{{x=y+5}atop{xy=-4}}right~y(y+5)=-4;~y^2+5y+4=0;}\\mathtt{(y+4)(y+1)=0toleft[begin{array}{ccc}mathtt{x_1=y_1+5=-4+5=1}\mathtt{x_2=y_2+5=-1+5=4}end{array}right}\\mathtt{OTBET:~(1;-4),~(4;-1).}$


$displaystylemathtt{left{{{x^2+y^2=29}atop{y^2-4x^2=9}}rightleft{{{y^2=29-x^2}atop{y^2=4x^2+9}}right~29-x^2=4x^2+9;~20=5x^2;}\\mathtt{x=б2~to~y=бsqrt{29-x^2}=бsqrt{29-(б2)^2}=бsqrt{29-4}=б5}\\mathtt{OTBET:~(б5;б4).}$