Toán Lớp 6: Tìm x,y a) ( 2x+1) (y-5)=12 b) 8+x=y(x+3) c) xy+2x+2y+4=10 n)2xy+x+y=17

Question

Toán Lớp 6:  Tìm x,y  a) ( 2x+1) (y-5)=12 b) 8+x=y(x+3) c) xy+2x+2y+4=10 n)2xy+x+y=17

diemchau · Answer

a)2x+1,y-5 l&agrave; ước của 12   &rArr;12=1.12=2.6=3.4   V&igrave; 2x+1 lẻ n&ecirc;n &rArr; 2x+1=1 hoặc 2x+1=3   TH1:2x+1=1&rArr;x=0,y-5=12&rArr;y=17   TH2:2x+1=3&rArr;x=1,y-5=4&rArr;y=9   Vậy x,y &isin; (0,17);(1,9)   b)  8+x=y(x+3)     &rArr;x+8=(x+3).y     &rArr;-(x+3).y+x+8=0     &rArr;-[(x+3).y-x-8]=0     &rArr;(x+3).y-x-8=0     &rArr;x+3=0     &rArr;x=-3     &rArr;y-1=0     &rArr;y=1     c)xy+2x+2y+4=10     &rArr;(x+2).y+2x+4=10     &rArr;(x+2).y+2x-10+4=0     &rArr;(x+2).y+2x-6=0     &rArr;x+2=0     &rArr;x=-2     &rArr;y+2=0     &rArr;y=-2

hoquyly · Answer

$ text{a)2x+1,y-5 l&agrave; ước của 12}$     $ text{&rArr;12=1.12=2.6=3.4}$     $ text{V&igrave; 2x+1 lẻ n&ecirc;n &rArr; 2x+1=1 hoặc 2x+1=3}$     $ text{TH1:2x+1=1&rArr;x=0,y-5=12&rArr;y=17}$     $ text{TH2:2x+1=3&rArr;x=1,y-5=4&rArr;y=9}$     $ text{Vậy x,y &isin; (0,17);(1,9)}$     $ text{b) 8+x=y(x+3)}$     $ text{&rArr;x+8=(x+3).y}$     $ text{&rArr;-(x+3).y+x+8=0}$     $ text{&rArr;-[(x+3).y-x-8]=0}$     $ text{&rArr;(x+3).y-x-8=0}$     &rArr;x+3=0     &rArr;x=-3     &rArr;y-1=0     &rArr;y=1     c)xy+2x+2y+4=10     &rArr;(x+2).y+2x+4=10     &rArr;(x+2).y+2x-10+4=0     &rArr;(x+2).y+2x-6=0     &rArr;x+2=0     &rArr;x=-2     &rArr;y+2=0     &rArr;y=-2     d)2xy+x+y=17     &rArr;(2x+1).y+x=17     &rArr;(2x+1).y+x-17=0     &rArr;2x+1=0     &rArr;2x=0-1=-1     &rArr;x=$ frac{-1}{2}$      &rArr;2y+1=0     &rArr;2y=-1     &rArr;y=$ frac{-1}{2}$