Answer: [tex]\lim_{x \to \infty} \dfrac{4x-1}{9+12x}\to \dfrac{1}{3}[/tex]
[tex]\lim_{x \to 4} \dfrac{x^2-x-12}{5x-20}\to\dfrac{7}{5} [/tex]
[tex]\lim_{x \to -\infty} \dfrac{5x+6}{4x+2}\to\dfrac{5}{4}[/tex]
[tex]\lim_{x \to 3} \dfrac{4x-12}{x^2-9}\to\dfrac{2}{3}[/tex]
Step-by-step explanation:
i) [tex]\lim_{x \to \infty} \dfrac{4x-1}{9+12x}[/tex]
Taking x as common outside from numerator and denominator , we have
[tex]\lim_{x \to \infty} \dfrac{x(4-\frac{1}{x})}{x(\frac{9}{x}+12)}\\\\=\lim_{x \to \infty} \dfrac{4-\frac{1}{x}}{\frac{9}{x}+12}\\\\=\dfrac{4-0}{0+12}=\dfrac{4}{12}=\dfrac{1}{3}[/tex]
ii) [tex]\lim_{x \to 4} \dfrac{x^2-x-12}{5x-20}[/tex]
It can be written as : [tex]\lim_{x \to 4} \dfrac{(x-4)(x+3)}{5(x-4)}[/tex]
[tex]=\lim_{x \to 4} \dfrac{x+3}{5}=\dfrac{4+3}{5}=\dfrac{7}{5}[/tex]
iii) [tex]\lim_{x \to -\infty} \dfrac{5x+6}{4x+2}[/tex]
Taking x as common outside from numerator and denominator , we have
[tex]\lim_{x \to -\infty} \dfrac{x(5+\frac{6}{x})}{x(4+\dfrac{2}{x})}\\\\=\dfrac{5+0}{4+0}=\dfrac{5}{4}[/tex]
iv) [tex]\lim_{x \to 3} \dfrac{4x-12}{x^2-9}[/tex]
which can be written as :
[tex]\lim_{x \to 3} \dfrac{4(x-3)}{(x-3)(x+3)}[/tex] ∵ [tex]a^2-b^2=(a+b)(a-b)[/tex]
[tex]=\lim_{x \to 3} \dfrac{4}{(x+3)}=\dfrac{4}{3+3}=\dfrac{4}{6}=\dfrac{2}{3}[/tex]