Đáp án:
Giải thích các bước giải:
Câu `7:`
`a) 2(x-3)-3(x-5)=4(3-x)-18`
`=> 2x-6-3x+15=12-4x-18`
`=> -x+9=-6-4x`
`=> -x+4x=-6-9`
`=> 3x=-15`
`=> x=-5`
`b) -2x-11 vdots 3x+2`
`=> 6x+33 vdots 3x+2`
`=> 2(3x+2)+29 vdots 3x+2`
`=> 29 vdots 3x+2`
`=> 3x+2 in Ư(29)={-29;-1;1;29}`
`=> 3x in {-31;-3;-1;27}`
`=> x in {-31/3;-1;-1/3;9}`
Mà `x in ZZ`
`=> x in {-1;9}`
`c) -112-56:x^2=-126`
`=> 56:x^2=(-112)-(-126)`
`=> 56:x^2=14`
`=> x^2=56:14`
`=> x^2=4`
`=> x=+-2`
`d) 2(x-7)-3(5-x)=-109`
`=> 2x-14-15+3x=-109`
`=> 5x-29=-109`
`=> 5x=(-109)+29`
`=> 5x=-80`
`=> x=-16`
`e) x-7 vdots x+6`
`=> x+6-13 vdots x+6`
`=> 13 vdots x+6`
`=> x+6 in Ư(13)={-13;-1;1;13}`
`=> x in {-19;-7;-5;7}`
