16: \(\left(x+3\right)^2-\left(x-4\right)\left(x+8\right)=1\)
=>\(x^2+6x+9-\left(x^2+8x-4x-32\right)=1\)
=>\(x^2+6x+9-\left(x^2+4x-32\right)=1\)
=>\(x^2+6x+9-x^2-4x+32=1\)
=>2x+41=1
=>2x=-40
=>x=-20
17: \(3\left(x-1\right)^2-3x\left(x-5\right)=1\)
=>\(3\left(x^2-2x+1\right)-3x^2+15x=1\)
=>\(3x^2-6x+3-3x^2+15x=1\)
=>9x=-2
=>x=-2/9
18: \(\left(x-2\right)^3-x^2\left(x-6\right)=4\)
=>\(x^3-6x^2+12x-8-x^3+6x^2=4\)
=>12x=12
=>x=1
19: \(3x\left(2-x\right)-2\left(x+1\right)\left(x-1\right)=5x\left(-x+3\right)\)
=>\(6x-3x^2-2\left(x^2-1\right)=-5x^2+15x\)
=>\(6x-3x^2-2x^2+2=-5x^2+15x\)
=>15x=6x+2
=>9x=2
=>x=2/9
20: \(\left(x-1\right)\left(x^2+x+1\right)-x^2\left(x-2\right)-2x^2+3x=7\)
=>\(x^3-1-x^3+2x^2-2x^2+3x=7\)
=>3x=8
=>x=8/3
21: \(3x-\left(x+1\right)\left(x^2-x+1\right)+x\cdot\left(x^2-4\right)=5\)
=>\(3x-x^3-1+x^3-4x=5\)
=>-x-1=5
=>-x=6
=>x=-6
