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a) \(x^3+9x^2+27x+27=\left(x+3\right)^3\)
b) \(3\sqrt{3x^3}+18x^2+12\sqrt{3x}+8=\left(\sqrt{3x}+2\right)^3\)
c) \(\dfrac{1}{4}-x^2=\left(\dfrac{1}{2}-x\right)\left(\dfrac{1}{2}+x\right)\)
\(=\left(x^2+2x\right)^2+9\left(x^2+2x\right)+20\)
\(=\left(x^2+2x+4\right)\left(x^2+2x+5\right)\)
=5(x2-\(\frac{18}{5}x\)-\(\frac{8}{5}\))=5(x2+\(\frac{2}{5}x-4x-\frac{8}{5}\))
=5(x-4)(\(\frac{2}{5}+x\))
\(4\left(x^2+15x+50\right)\left(x^2+18x+72\right)-3x^2\)
\(=4\left(x+5\right)\left(x+10\right)\left(x+12\right)\left(x+6\right)-3x^2\)
\(=4\left(x^2+17x+60\right)\left(x^2+16x+60\right)-3x^2\)
\(=4\left(x+60\right)^2+132x\left(x+60\right)+1088x^2-3x^2\)
\(=4\left(x+60\right)^2+132x\left(x+60\right)+1085x^2\)
\(=4\left(x+60\right)^2+62x\left(x+60\right)+70x\left(x+60\right)+1085x^2\)
\(=2\left(x+60\right)\left[2\left(x+60\right)+31x\right]+35x\left[2\left(x+60\right)+31x\right]\)
\(=\left(33x+120\right)\left(2x+120+35x\right)\)
\(=3\left(11x+40\right)\left(37x+120\right)\)
\(\Rightarrow\left(x^2+2x\right)^2+9\left(x^2+2x\right)+20=\left(x^2+2x\right)^2+4\left(x^2+2x\right)+5\cdot\left(x^2+2x\right)+20=\left(x^2+2x\right)\left(x^2+2x+4\right)+5\left(x^2+2x+4\right)=\left(x^2+2x+4\right)\left(x^2+2x+5\right)\)
a) \(2x^3-x^2+5x+3\)
\(=2x^3-2x^2+x^2+6x-x+3\)
\(=\left(2x^3-2x^2+6x\right)+\left(x^2-x+3\right)\)
\(=2x\left(x^2-x+3\right)+\left(x^2-x+3\right)\)
\(=\left(2x+1\right)\left(x^2-x+3\right)\)
b) \(27x^3-27x^2+18x-4\)
\(=27x^3-18x^2-9x^2+12x+6x-4\)
\(=\left(27x^3-18x^2+12x\right)-\left(9x^2-6x+4\right)\)
\(=3x\left(9x^2-6x+4\right)-\left(9x^2-6x+4\right)\)
\(=\left(3x-1\right)\left(9x^2-6x+4\right)\)
\(\left(x^2+2x\right)^2+4\left(x^2+2x\right)+5\left(x^2+2x\right)+20\)
\(=\left(x^2+2x\right)\left(x^2+2x+4\right)+5\left(x^2+2x+4\right)\)
\(=\left(x^2+2x+5\right)\left(x^2+2x+4\right)\)
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