Упр.39.6 ГДЗ Мордкович 7 класс (Алгебра)

• а) $$x^2y^2-1$$; б) $$25-36p^2c^2$$; в) $$4-c^2d^2$$; г) $$49x^2y^2-400$$.

1. $$x^2y^2-1=(xy)^2-1^2=(xy-1)(xy+1).$$
2. $$25-36p^2c^2=5^2-(6pc)^2=(5-6pc)(5+6pc).$$
3. $$4-c^2d^2=2^2-(cd)^2=(2-cd)(2+cd).$$
4. $$49x^2y^2-400=(7xy)^2-20^2=(7xy-20)(7xy+20).$$

Ответ

$$x^2y^2-1=(xy-1)(xy+1);$$
$$25-36p^2c^2=(5-6pc)(5+6pc);$$
$$4-c^2d^2=(2-cd)(2+cd);$$
$$49x^2y^2-400=(7xy-20)(7xy+20).$$