Đáp án:
a) (x,y)=(1,10),(-1,-12),(11,0),(-11,-2)
b) (x,y)=(3,3),(-5,-2)
c) (x,y)=(1,11),(13,-1),(-1,-15),(-13,-3)
Giải thích các bước giải:
a) 11=1.11=(-1).(-11)
suy ra x=1, $y+1=11 \Leftrightarrow y=10$
x=-1, $y+1=-11 \Leftrightarrow y=-12$
x=11, $y+1=1 \Leftrightarrow y=0$
x=-11, $y+1=-1 \Leftrightarrow y=-2$
vậy (x,y)=(1,10),(-1,-12),(11,0),(-11,-2)
b) 20=2.10=4.5=(-2).(-10)=(-4).(-5)
suy ra $x+1=2\Rightarrow x=1, 2y-1=10\Rightarrow 2y=11\Rightarrow y=\frac{11}{2} (loai)\\
x+1=10\Rightarrow x=9, 2y-1=2\Rightarrow 2y=3\Rightarrow y=\frac{3}{2} (loai)\\
x+1=-2\Rightarrow x=-3, 2y-1=-10\Rightarrow 2y=-9\Rightarrow y=\frac{-9}{2} (loai)\\
x+1=-10\Rightarrow x=-11, 2y-1=-2\Rightarrow 2y=-1\Rightarrow y=\frac{-1}{2} (loai)\\
x+1=4\Rightarrow x=3, 2y-1=5\Rightarrow 2y=6\Rightarrow y=3\\
x+1=-4\Rightarrow x=-5, 2y-1=-5\Rightarrow 2y=-4\Rightarrow y=-2\\
x+1=5\Rightarrow x=4, 2y-1=4\Rightarrow 2y=5\Rightarrow y=\frac{5}{2} (loai)\\
x+1=-5\Rightarrow x=-6, 2y-1=-4\Rightarrow 2y=-3\Rightarrow y=\frac{-3}{2} (loai)\\$
Vậy (x,y)=(3,3),(-5,-2)
c) $ x.y= 13-2x\Leftrightarrow x(y+2)=13\\
13=1.13=(-1).(-13)\\
x=1, y+2=13\Rightarrow y=11\\
x=13, y+2=1 \Rightarrow y=-1\\
x=-1, y+2=-13\Rightarrow y=-15\\
x=-13, y+2=-1 \Rightarrow y=-3\\$
vậy (x,y)=(1,11),(13,-1),(-1,-15),(-13,-3)
