Question

помогите пожалуйста, желательно побыстрей

Answer 1

Решение.

 Знаменатель дроби не может быть равен 0 .

$\bf1)\ \ 3x+4\ \ \to \ \ x\in R\\\\2)\ \ \dfrac{16}{a}\ \ \to \ \ a\ne 0\\\\3)\ \ \dfrac{8}{b-5}\ \ \to \ \ b-5\ne 0\ \ \to \ \ b\ne 5\\\\6)\ \ \dfrac{2}{x^2+1}\ \ \to \ \ x^2+1\ne 0\ \ \to \ \ x\in R\\\\7)\ \ \dfrac{3}{x^2-1}\ \ \to \ \ x^2-1\ne 0\ \ ,\ \ x^2\ne 1\ \ \to \ \ x\ne \pm 1\\\\8)\ \ \dfrac{4}{|x|-1}\ \ \to \ \ |x|-1\ne 0\ \ ,\ \ |x|\ne 1\ \ \to \ \ x\ne \pm 1\\\\11)\ \ \dfrac{1}{1+\frac{1}{x}}\ \ \to \ \ 1+\dfrac{1}{x}\ne 0\ \ ,\ \ \dfrac{x+1}{x}\ne 0\ \ \to \ \ x\ne 0\ ,\ x\ne -1$  

$\bf 12)\ \ \dfrac{4}{x-1}+\dfrac{7x}{x-4}\ \ \to \ \ x-1\ne 0\ ,\ x-4\ne 0\ \ \to \ \ x\ne 1\ ,\ x\ne 4\\\\13)\ \ \dfrac{7}{x(x-1)}\ \ \to \ \ x\ne 0\ ,\ x-1\ne 0\ \ \to \ \ x\ne 0\ ,\ x\ne 1$