Tìm các cặp số nguyên x, y sao cho:
a ) ( x – 3 ) ( y – 5 ) = 7.
b ) ( 2x + 1 ) . ( y – 1 ) = 3.
c ) ( x – 3 ) . ( 2 – y ) = 5.
Tìm các cặp số nguyên x, y sao cho: a ) ( x – 3 ) ( y – 5 ) = 7. b ) ( 2x + 1 ) . ( y – 1 ) = 3. c ) ( x – 3 ) . ( 2 – y ) = 5.
By Alexandra
a, (x-3)(y-5)=7
TH1: $\left \{ {{x-3=1} \atop {y-5=7}} \right.$ =>$\left \{ {{x=4} \atop {y=12}} \right.$
TH2: $\left \{ {{x-3=7} \atop {y-5=1}} \right.$ =>$\left \{ {{x=10} \atop {y=6}} \right.$
TH3: $\left \{ {{x-3=-1} \atop {y-5=-7}} \right.$ =>$\left \{ {{x=2} \atop {y=-2}} \right.$
TH4: $\left \{ {{x-3=-7} \atop {y-5=-1}} \right.$ =>$\left \{ {{x=-4} \atop {y=4}} \right.$
Vậy (x,y)∈{(4;12);(10;6);(2;-2);(-4;4)}
b, (2x+1)(y-1)=3
TH1: $\left \{ {{2x+1=1} \atop {y-1=3}} \right.$ =>$\left \{ {{x=…} \atop {y=…}} \right.$
TH2: $\left \{ {{2x+1=-1} \atop {y-1=-3}} \right.$ =>$\left \{ {{x=…} \atop {y=…}} \right.$
TH3: $\left \{ {{2x+1=3} \atop {y-1=1}} \right.$ =>$\left \{ {{x=…} \atop {y=…}} \right.$
TH4: $\left \{ {{2x+1=-3} \atop {y-1=-1}} \right.$ =>$\left \{ {{x=…} \atop {y=…}} \right.$
c, (x-3)(2-y)=5
TH1: $\left \{ {{x-3=1} \atop {2-y=5}} \right.$ =>$\left \{ {{x=…} \atop {y=…}} \right.$
TH2: $\left \{ {{x-3=-1} \atop {2-y=-5}} \right.$ =>$\left \{ {{x=…} \atop {y=…}} \right.$
TH3: $\left \{ {{x-3=5} \atop {2-y=1}} \right.$ =>$\left \{ {{x=…} \atop {y=…}} \right.$
TH4: $\left \{ {{x-3=-5} \atop {2-y=-1}} \right.$ =>$\left \{ {{x=…} \atop {y=…}} \right.$
Phần b và c tự tìm (x,y) nha bạn!!! Làm tương tự như phần a nhé!