Đáp án:
;-;
Giải thích các bước giải:
`1)x + 18 = 6 - 2x `
`→x+2x=6-18`
`→3x=-12`
`→x=-12:3`
`→x=-4`
Vậy `x=-4`
`2)17 - x = 7 - 6x`
`→-x+6x=7-17`
`→5x=-10`
`→x=-10:5`
`→x=-2`
Vậy `x=-2`
`3)(x+1).(x^2-4)=0`
`→` \(\left[ \begin{array}{l}x+1=0\\x^2-4=0\end{array} \right.\)
`→` \(\left[ \begin{array}{l}x=-1\\x=±2\end{array} \right.\)
Vậy `x∈{-1;2;-2}`
`4)11.|x-3|-20=3^3-(-5)^2`
`→11.|x-3|-20=27-25`
`→11.|x-3|-20=2`
`→11.|x-3|=22`
`→|x-3|=22:11`
`→|x-3|=2`
`→` \(\left[ \begin{array}{l}x-3=2\\x-3=-2\end{array} \right.\)
`→` \(\left[ \begin{array}{l}x=5\\x=1\end{array} \right.\)
Vậy `x∈{5;1}`