Question

Решите неравенство x-2y=1 xy+y=12

Answer 1

$x-2y=1\\ xy+y=12\\\\ x-2y=1\\ xy+y+x+1=13+x\\ \\ x-2y=1\\ (x+1)(y+1)=13+x\\ \\ x=1+2y\\ (2+2y)(y+1)=14+2y\\ 2(y+1)^2=2(7+y)\\ (y+1)^2=7+y\\ y^2+2y+1=7+y \\ y^2+y-6=0\\ D=5^2\\ y=2\\ y=-3\\ x=5\\ y=-5$