Teorema de la media o Valor medio para integrales
Si una función es continua en un intervalo cerrado
, entonces existe un punto
en el interior del intervalo tal que:
![Rendered by QuickLaTeX.com {[a,b]}](https://www.superprof.es/apuntes/wp-content/ql-cache/quicklatex.com-d044b1a602eecc21269dece407599734_l3.png)
![Rendered by QuickLaTeX.com {c}](https://www.superprof.es/apuntes/wp-content/ql-cache/quicklatex.com-e4ba7dc168959e1f6358b4bc982168d2_l3.png)
![Rendered by QuickLaTeX.com {\displaystyle\int_{a}^{b}f(x) \, dx=(b-a)\cdot f(c)}](https://www.superprof.es/apuntes/wp-content/ql-cache/quicklatex.com-cb2581a11a94c79435d29e94b1189cc2_l3.png)
![grafica de una funcion continua](https://www.superprof.es/apuntes/wp-content/uploads/2019/05/teorema-fundamental-del-calculo-15.gif)
Ejemplo:
Hallar el valor de
del teorema de la media, para la función
en el intervalo
.
![Rendered by QuickLaTeX.com {c}](https://www.superprof.es/apuntes/wp-content/ql-cache/quicklatex.com-e4ba7dc168959e1f6358b4bc982168d2_l3.png)
![Rendered by QuickLaTeX.com {f(x)=3x^{2}}](https://www.superprof.es/apuntes/wp-content/ql-cache/quicklatex.com-af05bdb81065d8fd0145570280eb7e44_l3.png)
![Rendered by QuickLaTeX.com {[-4,-1]}](https://www.superprof.es/apuntes/wp-content/ql-cache/quicklatex.com-19e667ff17c9fb8912222a347f1cce71_l3.png)
1Calculamos el resultado de la integral definida
![Rendered by QuickLaTeX.com {\displaystyle\int_{-4}^{-1}3x^{2} \, dx= \left. x^{3}\right |_{-4}^{-1}=-1+64=63}](https://www.superprof.es/apuntes/wp-content/ql-cache/quicklatex.com-a12a91afbea46cbacd222c913506625d_l3.png)
2Como la función es continua en el intervalo
, se puede aplicar el teorema de la media.
![Rendered by QuickLaTeX.com {[-4,-1]}](https://www.superprof.es/apuntes/wp-content/ql-cache/quicklatex.com-19e667ff17c9fb8912222a347f1cce71_l3.png)
![Rendered by QuickLaTeX.com {\begin{array}{rcl}63&=&[-1-(-4)]\cdot f(c) \\ && \\ 21 &=& f(c) \end{array}}](https://www.superprof.es/apuntes/wp-content/ql-cache/quicklatex.com-b45b527806d8ccb4a059f55b76743e9b_l3.png)
3El valor de
, el cual sustituimos en la igualdad anterior y despejamos ![Rendered by QuickLaTeX.com {c}](https://www.superprof.es/apuntes/wp-content/ql-cache/quicklatex.com-e4ba7dc168959e1f6358b4bc982168d2_l3.png)
![Rendered by QuickLaTeX.com {f(c)=3c^{2}}](https://www.superprof.es/apuntes/wp-content/ql-cache/quicklatex.com-f98d53bea8b94508efd254857841a544_l3.png)
![Rendered by QuickLaTeX.com {c}](https://www.superprof.es/apuntes/wp-content/ql-cache/quicklatex.com-e4ba7dc168959e1f6358b4bc982168d2_l3.png)
![Rendered by QuickLaTeX.com {\begin{array}{rcl}21 &=& 3c^{2} \\ && \\ 7 &=& c^{2} \\ && \\ \pm\sqrt{7}&=& c \end{array}}](https://www.superprof.es/apuntes/wp-content/ql-cache/quicklatex.com-8ecfade53c6d339446b07ab593cbde23_l3.png)
La solución positiva no es válida porque no pertenece al intervalo.
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