$a)_{}$ $4x^4-12x^2+1_{}$
$=4x^4-8x^3+8x^3+2x^2-16x^2+2x^2+4x-4x+1_{}$
$=2x^2.(2x^2-4x+1)+4x.(2x^2-4x+1)+2x^2-4x+1_{}$
$=(2x^2-4x+1)(2x^2+4x+1)_{}$
$b)_{}$ $x^3-5x^2-14x_{}$
$=x.(x^2-5x-14){}$
$=x.(x^2+2x-7x-14)_{}$
$=x. [ x.(x+2)-7.(x+2)] _{}$
$=x.(x+2)(x-7)_{}$
$c)_{}$ $x^4-7x^2+1_{}$
$=x^4-3x^3+3x^3+x^2-9x^2+x^2+3x-3x+1_{}$
$=x^2.(x^2-3x+1)+3x.(x^2-3x+1)+x^2-3x+1_{}$
$=(x^2-3x+1)(x^2+3x+1)_{}$
