Răspuns:
Explicație pas cu pas:
[tex]a)~x^{4}-a^{2}=(x^{2})^{2}-a^{2}=(x^{2}-a)(x^{2}+a)\\b)~9x^{4}-25=(3x^{2})^{2}-5^{2}=(3x^{2}-5)(3x^{2}+5)\\c)~\frac{1}{4} -a^{2}=(\frac{1}{2})^{2}-a^{2}=(\frac{1}{2}-a)(\frac{1}{2}+a)\\d)~y^{2}-\frac{16}{25} z^{2}=y^{2}-(\frac{4}{5} z)^{2}=(y-\frac{4}{5} z)(y+\frac{4}{5} z)\\e)~\frac{x^{2}}{9}-\frac{9y^{2}}{49}=(\frac{x}{3})^{2}-(\frac{3y}{7})^{2}=(\frac{x}{3}-\frac{3y}{7}) (\frac{x}{3}+\frac{3y}{7})\\ f)~\frac{1}{81}a^{2}b^{2}c^{2} -4=(\frac{1}{9}abc)^{2}-2^{2}=(\frac{1}{9}abc-2) (\frac{1}{9}abc+2)[/tex]
La toate se aplică formula a²-b²=(a-b)(a+b)
