Question

Bài 3 : Tìm số nguyên x , biết

a ) 4 x - 15 = -75 - x 

b ) I2x -7I + 2 = 13

Answer 1

a: =>5x=-60

hay x=-12

b: =>|2x-7|=11

=>2x-7=11 hoặc 2x-7=-11

=>2x=18 hoặc 2x=-4

=>x=9 hoặc x=-2

Answer 2

`a ) 4 x - 15 = -75 - x `

`=> 4x + x = -75 +15`

`<=> 5x = -60`

`=> x = -60/5 = -12`

Vậy `x=-12`

`b ) |2x -7| + 2 = 13`

`<=>|2x-7| = 13 - 2`

`<=>|2x-7| = 11`

`<=>`\(\left[{}\begin{matrix}2x-7=11\\2x-7=-11\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}2x=18\\2x=-4\end{matrix}\right.\)

`<=>`\(\left[{}\begin{matrix}x=9\\x=-2\end{matrix}\right.\)

Vậy \(\left[{}\begin{matrix}x=9\\x=-2\end{matrix}\right.\)

Answer 3

\(4x-15=-75-x\)

\(4x+x=-75+15\)

\(5x=-60\)

`=>x=-12`

b) \(\left|2x-7\right|+2=13\)

\(\left|2x-7\right|=13-2=11\)

\(2x-7=11\)

`=>`\(\left[{}\begin{matrix}2x-7=11\\2x-7=-11\end{matrix}\right.\)

\(\left[{}\begin{matrix}2x=18\\2x=-4\end{matrix}\right.\)

\(x=\left[{}\begin{matrix}\dfrac{18}{2}=9\\-\dfrac{4}{2}=-2\end{matrix}\right.\)