${a) 16x² - 8x + 1
= (4x)² - 2.4x.1 + 1²
= (2x + 1)²}$
${b) x² + 5x + \frac{25}{4}
= x² + 2.x.\frac{5}{2} + (\frac{25}{4} )²
= (x + \frac{5}{2} ) ²}$
${c) 4x² + 12xy + 9y²
= (2x)² + 2.2x.3y + (3y)²
= (2x + 3y)²}$
${d) x³ + 3yx² + 3x +1
= ( x+1 )³}$
${e) 27y³ - 9y² + y - \frac{1}{27}
= (3y - \frac{1}{3} )³ }$