5)
$(x-2)^{3}$ - (x-4)($x^{2}$ + $4x$ + $16$ ) + $6(x+1)^{2}$ =$49$
`=>` $x^{3}$ - $6x^{2}$ + $12x$ - $8$ - ( $x^{3}$ - $64$) +$6x^{2}$ + $12x$ + $6$ $=$ $49$
`=>` $24x$ + $62$ = $49$
`=>` $24x$ = $13$
`=>` $x$= $\frac{13}{24}$
6)
$(x+2)$($x^{2}$ - $2x$ +$4$) - $x$($x^{2}$ + $2$) $=$ $15$
`=>` $x^{3}$ + $8$ - $x^{3}$ - $2x$ $=$ $15$
`=>` $2x$ $=$ $8-15=-7$
`=>` $x = -\frac{7}{2}$
7)
$3x(2x-4) - (6x-1)(x+2) = 25$
`=>` $6x^{2}$ $-12x - $ ($6x^{2}$ $+ 11x -2)=25$
`=>` $-23x +2 = 25$
`=>` $-23x = 23$
`=>` $x=-1$
8)
$(x+1)(x+2) -(x+2)(x+5)=2$
`=>` $x^{2}$ $+ 4x +3 -$ $x^{2}$ $- 7x -10=2$
`=>` $-3x -7=2$
`=>` $-3x= 2-7=-5$
`=>` $x=$ $\frac{5}{3}$
