`b) 4x -5+2.(2x -3.(x-4) )=27`
`⇔4x -5 +2.(2x -3x +12) =27`
`⇔4x -5 +2.(-x+12) =27`
`⇔4x -5 -2x +24 =27`
`⇔2x +19 =27`
`⇔2x =8`
`⇔x =4`
`c)2x.(x² +x-8) -(x+3).(2x-1) =3.(1-x)`
`⇔2x³ +2x² -16x -(2x² +5x -3) =3 -3x`
`⇔2x³ +2x² -16x -2x² -5x +3 -3+3x=0`
`⇔2x³ -18x =0`
`⇔2x.(x²-9)=0`
`<=>` \(\left[ \begin{array}{l}2x = 0\\x^2 - 9 = 0\end{array} \right.\)
`<=>` \(\left[ \begin{array}{l}x=0\\x=±3\end{array} \right.\)
