Question

tìm số nguyên xy thỏa mãn (x+1)(2y-5)=8

Answer 1

( x + 1 ) ( 2y - 5 ) = 8

=> ( x + 1 ) ( 2y - 5 ) = 1 . 8 = 8 . 1 = 2 . 4 = 4 . 2 = ( -1 ) . ( -8 ) = ( -8 ) . ( -1 ) = ( -2 ) . ( -4 ) = ( -4 ) . ( -2 )

lập bảng ta có :

x + 1	1	8	2	4	-1	-8	-2	-4
2y - 5	8	1	4	2	-8	-1	-4	-2
x	0	7	1	3	-2	-9	-3	-5
y	\(\frac{13}{2}\)	3	\(\frac{9}{2}\)	\(\frac{7}{2}\)	\(\frac{-3}{2}\)	2	\(\frac{1}{2}\)	\(\frac{3}{2}\)

Vậy ( x ; y ) = ( 7 ; 3 ) = ( -9 ; 2 )

Answer 2

xy=73