El tercer termino de una sucesion geometrica es 54 y el quinto termino es 486?

El tercer termino de una sucesióngeométricaes 54 y el quinto termino es 486.

Encontrar el segundo termino

<img src="https://tex.z-dn.net/?f=a_%7B2%7D%3D%20%20%20x%0A%0A%0Aa_%7B3%7D%3D%2054%0A%0Aa_%7B5%7D%3D486" />

<img src="https://tex.z-dn.net/?f=a_%7B3%7D%3D%2054%0A%0A54%3Dar%20%5E%7B3-1%7D%20%0A%0Aa%3D%2054%2Fr%5E%7B2%7D%20.................%281%29" />

<img src="https://tex.z-dn.net/?f=a_%7B5%7D%3D486%0A%0A%0A486%20%3D%20ar%5E%7B5-1%7D%0A%0Aa%3D%20486%20%2Fr%5E%7B4%7D%20.......%282%29" />

<img src="https://tex.z-dn.net/?f=%5Cfrac%7B54%7D%7Br%5E2%7D%3D%5Cfrac%7B486%7D%7Br%5E4%7D" />

<img src="https://tex.z-dn.net/?f=54r%5E4%3Dr%5E2%5Ccdot%20%5C%3A486" />

<img src="https://tex.z-dn.net/?f=54r%5E4-r%5E2%5Ccdot%20%5C%3A486%3Dr%5E2%5Ccdot%20%5C%3A486-r%5E2%5Ccdot%20%5C%3A486" />

<img src="https://tex.z-dn.net/?f=54r%5E4-486r%5E2%3D0%0A%0A%5Cmathrm%7BRe-escribir%5C%3Ala%5C%3Aecuacion%5C%3Acon%5C%3A%7Du%3Dr%5E2%5Cmathrm%7B%5C%3Ay%5C%3A%7Du%5E2%3Dr%5E4" />

<img src="https://tex.z-dn.net/?f=54u%5E2-486u%3D0%0A%0A%0A" />

<img src="https://tex.z-dn.net/?f=%5Cmathrm%7BPara%5C%3Auna%5C%3Aecuacion%5C%3Ade%5C%3Asegundo%5C%3Agrado%5C%3Ade%5C%3Ala%5C%3Aforma%5C%3A%7Dax%5E2%2Bbx%2Bc%3D0" />

<img src="https://tex.z-dn.net/?f=x_%7B1%2C%5C%3A2%7D%3D%5Cfrac%7B-b%5Cpm%20%5Csqrt%7Bb%5E2-4ac%7D%7D%7B2a%7D" />

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