Asosiy tarkibga o'tish

1.2-bo'lim : Teskari funksiyalar

5. \(W\left( x \right) = \sqrt[5]{{9 - 11x}}\) uchun teskarisini toping. Ushbu bo'limda muhokama qilinganidek, kompozitsiyadan birini yoki ikkalasini hisoblash orqali teskarisini tekshiring.

Yechim
\[y = \sqrt[5]{{9 - 11x}}\]
2-qadam
\[x = \sqrt[5]{{9 - 11y}}\]
3-qadam
\[\begin{align*}x & = \sqrt[5]{{9 - 11y}}\\ {x^5} & = 9 - 11y\\ & {x^5} - 9 = - 11y\\ y &= - \frac{1}{{11}}\left( {{x^5} - 9} \right)\hspace{0.25in}\hspace{0.25in}\,\,\,\, \to \hspace{0.25in}\hspace{0.25in}\require{bbox} \bbox[2pt,border:1px solid black]{{{W^{ - 1}}\left( x \right) = \frac{1}{{11}}\left( {9 - {x^5}} \right)}}\end{align*}\]

E'tibor bering, biz minus belgisini qavs ichiga ko'paytirdik. Agar minus belgisi oldinda qolsa, uni yo'qotmaslik uchun buni qildik. Buning teskarisini olish uchun buni qilish shart emas.

Va nihoyat, ishimizni tekshirish uchun \(\left( {W \circ {W^{ - 1}}} \right)\left( x \right)\) yoki \(\left( {{W^{ - 1}} \circ W} \right)\left( x \right)\) hisoblang.

4-qadam

Ikkala kompozitsiya ham bajarilishi mumkin, keling, bu holda \(\left( {{W^{ - 1}} \circ W} \right)\left( x \right)\) ni bajaraylik.

\[\begin{align*}\left( {{W^{ - 1}} \circ W} \right)\left( x \right) & = {W^{ - 1}}\left[ {W\left( x \right)} \right]\\ & = \frac{1}{{11}}\left( {9 - {{\left[ {\sqrt[5]{{9 - 11x}}} \right]}^5}} \right)\\ & = \frac{1}{{11}}\left( {9 - \left[ {9 - 11x} \right]} \right)\\ & = \frac{1}{{11}}\left( {11x} \right)\\ & = x\end{align*}\]

Shunday qilib, biz \(x\)-ni kompozitsiyadan chiqardik va shuning uchun biz o'z ishimizni to'g'ri bajarganimizni bilamiz.