a: \(\Leftrightarrow\left(x,y+1\right)\in\left\{\left(1;5\right);\left(5;1\right);\left(-1;-5\right);\left(-5;-1\right)\right\}\)
hay \(\left(x,y\right)\in\left\{\left(1;4\right);\left(5;0\right);\left(-1;-6\right);\left(-5;-2\right)\right\}\)
b: \(\Leftrightarrow xy+x+y+1=3\)
\(\Leftrightarrow\left(y+1\right)\left(x+1\right)=3\)
\(\Leftrightarrow\left(x+1;y+1\right)\in\left\{\left(1;3\right);\left(3;1\right);\left(-1;-3\right);\left(-3;-1\right)\right\}\)
hay \(\left(x,y\right)\in\left\{\left(0;2\right);\left(2;0\right);\left(-2;-4\right);\left(-4;-2\right)\right\}\)
c: \(\Leftrightarrow xy+5y-3x-15=15\)
\(\Leftrightarrow\left(x+5\right)\left(y-3\right)=15\)
\(\Leftrightarrow\left(x+5;y-3\right)\in\left\{\left(1;15\right);\left(15;1\right);\left(-1;-15\right);\left(-15;-1\right);\left(3;5\right);\left(5;3\right);\left(-3;-5\right)\right\}\)
\(\Leftrightarrow\left(x,y\right)\in\left\{\left(-4;18\right);\left(10;4\right);\left(-6;-12\right);\left(-20;2\right);\left(-2;8\right);\left(0;6\right);\left(-8;-2\right);\left(-10;0\right)\right\}\)
Mình hướng dẫn cậu làm câu `a`, các câu còn lại mình làm tắt nha.
`a, x(y+1) = 5`
`-> x in Ư(5)`
`-> x in {+-1, +-5}`
`x = 1 -> y = 4`
`x = -1 -> y = -6`
`x = 5 -> y = 0`
`x = -5 -> y = -2`
`b, xy + x + y = 2`
`x(y+1) + y+1 = 1`
`= (x+1)(y+1) =1`
`-> x+1 in Ư(1)`
`-> x + 1 in {+-1}`
`x = 1 -> y = 0`
`x = -2 -> y = -2`
`c, xy + 5y - 3x = 30`
`y(x+5) - 3(x+5) = 45`
`-> (y-3)(x+5) = 45`
`-> y - 3 in Ư(45)`
`...`
