Toán Lớp 6: tìm các số tự nhiên x,y biết 2xy + x + 2y = 13
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Toán Lớp 6: tìm các số tự nhiên x,y biết 2xy + x + 2y = 13
Comments ( 1 )
=>x(2y+1)+2y=13
=>x(2y+1)+2y+1=13+1
=>x(2y+1)+(2y+1)=14
=>(x+1)(2y+1)=14
Ta có : 14=1.14=14.1=2.7=7.2
Ta có bảng sau :
$\begin{array}{|c|c|c|}\hline \text{x+1}&\text{1}&\text{14}&\text{2}&\text{7}\\\hline \text{2y+1}&\text{14}&\text{1}&\text{7}&\text{2}\\\hline \text{x}&\text{0}&\text{13}&\text{1}&\text{6}\\\hline \text{y}&\dfrac{13}{2}(KTM)&\text{0}&\text{3}&\dfrac{1}{2}(KTM)\\\hline \end{array}$
Vậy (x;y)∈{(13;0);(1;3)}