a: \(\left(x+2\right)^3-\left(x-3\right)\left(x^2+3x+9\right)=\left(2x-3\right)\left(3x+2\right)\)
=>\(x^3+6x^2+12x+8-\left(x^3-27\right)=6x^2+4x-9x-6\)
=>\(x^3+6x^2+12x+8-x^3+27=6x^2-5x-6\)
=>\(6x^2+12x+35=6x^2-5x-6\)
=>12x+35=-5x-6
=>17x=-41
=>\(x=-\frac{41}{17}\)
b: \(\left(x+2\right)\left(x^2-2x+4\right)-\left(x-3\right)^3=\left(3x+1\right)\left(3x-1\right)\)
=>\(x^3+8-\left(x^3-9x^2+27x-27\right)=9x^2-1\)
=>\(x^3+8-x^3+9x^2-27x+27=9x^2-1\)
=>\(9x^2-27x+35=9x^2-1\)
=>-27x+35=-1
=>-27x=-36
=>\(x=\frac{36}{27}=\frac43\)
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