Question

Mọi người ơi cho mình hỏi bài này với 

Tìm x thuộc Z:

A)\(\dfrac{x-1}{9}=\dfrac{8}{3}\)    B)\(\dfrac{-x}{4}=\dfrac{-9}{x}\)    C)\(\dfrac{x}{4}=\dfrac{18}{x+1}\)

Answer 1

a: =>x-1=24

hay x=25

b: =>x²=36

=>x=6 hoặc x=-6

c: =>x(x+1)=72

=>x=8 hoặc x=-9

Answer 2

Tk

a: =>x-1=24

hay x=25

b: =>x²=36

=>x=6 hoặc x=-6

c: =>x(x+1)=72

=>x=8 hoặc x=-9

Answer 3

\(a,\dfrac{x-1}{9}=\dfrac{8}{3}\)

\(\left(x-1\right).3=8.9\)

\(\left(x-1\right).3=72\)

\(x-1=72:3=24\)

\(x=24+1=25\)

 

\(b,\dfrac{-x}{4}=\dfrac{-9}{x}\)

\(\left(-x\right).x=\left(-9\right).4\)

\(-\left(x\right)^2=-36\)

\(-\left(x\right)^2=-\left(6\right)^2\)

 

\(c,\dfrac{x}{4}=\dfrac{18}{x+1}\)

\(x.\left(x+1\right)=18.4\)

\(x^2+x=72\)

\(2x^2=72\)

\(x^2=72:2=36\)

\(x^2=6^2\)

\(x=6\)