Đáp án:
$a/ 4x^{2} - 1$
$= (2x)^{2} - 1^{2}$
$= (2x - 1)(2x + 1)$
$b/ 25a^{2} - 0,01$
$= (5a)^{2} - 0.1^{2}$
$= (5a - 0,1)(5a + 0.1)$
$c/ 9x^{4} - \frac{1}{4}$
$= (3x^{2})^{2} - (\frac{1}{2})^{2}$
$= (3x^{2} - \frac{1}{2})(3x^{2} + \frac{1}{2}$)
$d/ a^{4} - b^{4}$
$= (a^{2})^{2} - (b^{2})^{2}$
$= (a^{2} - b^{2})(a^{2} + b^{2}$)
$= (a - b)(a + b)(a^{2} + b^{2})$
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