Question

помогите решить два задания ​

Answer 1

$I ) \displaystyle \left \{\begin{array}{ccc} xy-y=24 \\\\x-3y=-5 \end{array } \right.\to \left \{\begin{array}{ccc} xy-y=24 \\\\ \!\!x=3y-5 \end{array } \right. \to \\\\\\(3y-5)y-y=24 \\\\3y^2-5y-y-24=0 \\\\3y^2-6y-24=0 \ \ | \div3 \\\\y^2-2y-8=0 \\\\\left \{ {{y_1+ y_2=2} \atop {y_1\cdot y_2=-8 }} \right. \to \ \ y_1=4 \ \ ; \ \ y_2=-2 \\\\ . \qquad \qquad \qquad \ \ \ \ \ \ \ x_1=7 \ \ ; \ \ x_2=-11 \\\\\ Otvet : \ \ (7 \ ; \ 4 ) \ \ u \ \ (-11 \ ; \ -2)$

$II ) \displaystyle P=18 cm \\\\ S=20cm^2 \\\\\left \{ {{P=2(a+b)} \atop {\!\!\!\!\!\!\!\!\!\!\!S=ab}} \right. \to \left \{ {{2(a+b)=18} \atop {\!\!\!\!\!\!\!\!\!ab=20 }} \right.\to \left \{ {{a+b=9} \atop {ab=20 }} \right. - Teorema \ \ Vieta \\\\\\ a=4 \ \ ; \ \ b=5 \ \ ili \ \ a=5 \ \ ; \ \ b=4 \\\\ Otvet : 4 \ u \ 5 \ \ ili \ \ 5 \ u \ 4$