Asosiy tarkibga o'tish

2.7-bo'lim : Infinity chegaralari, I qism

1. \(f\left( x \right) = 4{x^7} - 18{x^3} + 9\) uchun quyidagi chegaralarning har birini baholang.

  1. \(\mathop {\lim }\limits_{x \to \, - \infty } f\left( x \right)\)
  2. \(\mathop {\lim }\limits_{x \to \,\infty } f\left( x \right)\)
a \(\mathop {\lim }\limits_{x \to \, - \infty } f\left( x \right)\) Yechim

Buni amalga oshirish uchun biz qilishimiz kerak bo'lgan yagona narsa \(x\) ning eng katta kuchini butun ko'phaddan ajratib ko'rsatish va keyin asosiy chegara xususiyatlaridan foydalanish. 1-fakt limitni hisoblash uchun ushbu bo'limdan.

\[\begin{align*}\mathop {\lim }\limits_{x \to \, - \infty } \left( {4{x^7} - 18{x^3} + 9} \right) & = \mathop {\lim }\limits_{x \to \, - \infty } \left[ {{x^7}\left( {4 - \frac{{18}}{{{x^4}}} + \frac{9}{{{x^7}}}} \right)} \right]\\ & = \left( {\mathop {\lim }\limits_{x \to \, - \infty } {x^7}} \right)\left[ {\mathop {\lim }\limits_{x \to \, - \infty } \left( {4 - \frac{{18}}{{{x^4}}} + \frac{9}{{{x^7}}}} \right)} \right] = \left( { - \infty } \right)\left( 4 \right) = \require{bbox} \bbox[2pt,border:1px solid black]{{ - \infty }}\end{align*}\]

b \(\mathop {\lim }\limits_{x \to \,\infty } f\left( x \right)\) Yechim

Ushbu qism uchun biz birinchi qismda qilgan barcha matematik manipulyatsiyalar chegaraning o'ziga bog'liq emas edi va shuning uchun bu erda takrorlash shart emas. Biz muammoni chegaralarni olishimizdan oldin hal qilishimiz va keyin davom etishimiz mumkin.

\[\mathop {\lim }\limits_{x \to \,\infty } \left( {4{x^7} - 18{x^3} + 9} \right) = \left( {\mathop {\lim }\limits_{x \to \,\infty } {x^7}} \right)\left[ {\mathop {\lim }\limits_{x \to \,\infty } \left( {4 - \frac{{18}}{{{x^4}}} + \frac{9}{{{x^7}}}} \right)} \right] = \left( \infty \right)\left( 4 \right) = \require{bbox} \bbox[2pt,border:1px solid black]{\infty }\]