Asosiy tarkibga o'tish

2.9-bo'lim : Davomiylik

1. \(f\left( x \right)\) ning grafigi quyida keltirilgan. Ushbu grafik asosida funktsiyaning qayerda uzluksiz ekanligini aniqlang.

The graph of \(f\left( x \right)\) on \( - 6 \le x \le 5\).  Starting at the left the graph increases to a peak at approximately \(\left( { - 5,4} \right)\) and then decreases to a closed dot at \(\left( { - 4,3} \right)\).  There is an open dot at \(\left( { - 4, - 2} \right)\) and from there the graph increases to a closed dot at \(\left( { - 1,4} \right)\).  The graph continues on from that point up to a peak at approximately \(\left( {1,5} \right)\) and then falls steeply to a closed dot at \(\left( {2, - 1} \right)\).  There is an open dot at \(\left( {2,5} \right)\) and from there the graph rises to a peak at approximately \(\left( {3,6} \right)\) and then decreases to an open dot at \(\left( {4,2} \right)\).  The graph then continues on down from that point, leaving the bottom of the graph at approximately \(x = 5\).
Yechim

Yechimni boshlashdan oldin, \(x = a\) da funksiya uzluksiz bo‘lishi uchun \(f\left( a \right)\) ham, \(\mathop {\lim }\limits_{x \to a} f\left( x \right)\) ham mavjud bo‘lishi va bizda quyidagilar bo‘lishi kerakligini esga oling:

\[\mathop {\lim }\limits_{x \to a} f\left( x \right) = f\left( a \right)\]

Ushbu fikrdan foydalanib, funktsiyaning doimiy emasligi aniq bo'lishi kerak.

Birinchidan, \(x = - 4\) da bizda borligiga e'tibor bering,

\[\mathop {\lim }\limits_{x \to - {4^ - }} f\left( x \right) = 3 \ne - 2 = \mathop {\lim }\limits_{x \to - {4^ + }} f\left( x \right)\]

va shuning uchun biz \(\mathop {\lim }\limits_{x \to - 4} f\left( x \right)\) mavjud emasligini ham bilamiz. Shunday qilib, biz \(f\left( x \right)\) degan xulosaga kelishimiz mumkin uzluksiz \(x = - 4\) da, chunki limit mavjud emas.

Xuddi shunday, \(x = 2\) da bizda,

\[\mathop {\lim }\limits_{x \to {2^ - }} f\left( x \right) = - 1 \ne 5 = \mathop {\lim }\limits_{x \to {2^ + }} f\left( x \right)\]

va shuning uchun biz \[\mathop {\lim }\limits_{x \to 2} f\left( x \right)\] mavjud emasligini ham bilamiz. Shunday qilib, yana, limit mavjud emasligi sababli, biz \(f\left( x \right)\) ekanligini ko'rishimiz mumkin uzluksiz at \(x = 2\).

Nihoyat, \(x = 4\) ni ko'rib chiqaylik. Bu erda biz buni ko'rishimiz mumkin,

\[\mathop {\lim }\limits_{x \to {4^ - }} f\left( x \right) = 2 = \mathop {\lim }\limits_{x \to {4^ + }} f\left( x \right)\]

va shuning uchun biz \(\mathop {\lim }\limits_{x \to 4} f\left( x \right) = 2\) ekanligini ham bilamiz. Biroq, biz \(f\left( 4 \right)\) mavjud emasligini ham ko'rishimiz mumkin va shuning uchun yana bir bor \(f\left( x \right)\) uzluksiz \(x = 4\) da, chunki bu safar funksiya \(x = 4\) da mavjud emas.

Ushbu grafikdagi boshqa barcha nuqtalar funksiya va chegara mavjud bo'ladi va bizda \(\mathop {\lim }\limits_{x \to a} f\left( x \right) = f\left( a \right)\) bo'ladi va shuning uchun doimiy bo'ladi.

Xulosa qilib aytganda, ushbu grafik uchun uzilish nuqtalari: \(x = - 4\), \(x = 2\) va \(x = 4\).