Упр.15.3 ГДЗ Мерзляк Поляков 7 класс (Алгебра)

1) (c-2)(c+2); 2) (12-x)(12+x);
3) (3x+y)(3x-y); 4) (6x-9)(6x+9);
5) (x+7)(7-x); 6) (5a-8b)(5a+8b);
7) (8m+2)(2-8m); 8) (13c-14d)(14d+13c).

1. $$ (c-2)(c+2)=c^2-2^2=c^2-4 $$
2. $$ (12-x)(12+x)=12^2-x^2=144-x^2 $$
3. $$ (3x+y)(3x-y)=(3x)^2-y^2=9x^2-y^2 $$
4. $$ (6x-9)(6x+9)=(6x)^2-9^2=36x^2-81 $$
5. $$ (x+7)(7-x)=(7+x)(7-x)=7^2-x^2=49-x^2 $$
6. $$ (5a-8b)(5a+8b)=(5a)^2-(8b)^2=25a^2-64b^2 $$
7. $$ (8m+2)(2-8m)=(2+8m)(2-8m)=2^2-(8m)^2=4-64m^2 $$
8. $$ (13c-14d)(14d+13c)=(13c-14d)(13c+14d)=(13c)^2-(14d)^2=169c^2-196d^2 $$

Ответ

1) $$c^2-4$$; 2) $$144-x^2$$; 3) $$9x^2-y^2$$; 4) $$36x^2-81$$; 5) $$49-x^2$$; 6) $$25a^2-64b^2$$; 7) $$4-64m^2$$; 8) $$169c^2-196d^2$$.