En resumen

(1)<img src="https://tex.z-dn.net/?f=211_x%3D21%20" /> <img src="https://tex.z-dn.net/?

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Rdmoraes6947
8

(1)<img src="https://tex.z-dn.net/?f=211_x%3D21%20" />

<img src="https://tex.z-dn.net/?f=2x%5E2%2Bx%2B1%3D21%5C%5C%20%5C%5C%0A2x%5E2%2Bx-20%3D0%5C%5C%20%5C%5C%0Ax%3D%5Cdfrac%7B-2%5Cpm%5Csqrt%7B161%7D%7D%7B4%7D%5Cnotin%20%5Cmathbb%7BN%7D" />

(2) Primera suposición<img src="https://tex.z-dn.net/?f=2%2811%29_x%3D21" />

<img src="https://tex.z-dn.net/?f=2x%2B11%3D21%5Cwedge%20x%5C%20%5Ctextgreater%20%5C%2011%5C%5C%0Ax%3D5%5Cwedge%20x%5C%20%5Ctextgreater%20%5C%2011%5C%5C%0Ax%5Cin%5Cemptyset" />

(3) Segunda suposición<img src="https://tex.z-dn.net/?f=%2821%291_x%3D21" />

<img src="https://tex.z-dn.net/?f=21x%2B1%3D21%5Cwedge%20x%5C%20%5Ctextgreater%20%5C%2021%5C%5C%20%0Ax%3D20%2F21%5Cwedge%20x%5C%20%5Ctextgreater%20%5C%2021%5C%5C%20%0Ax%5Cin%5Cemptyset" />

Conclusión : Ejercicio mal propuesto.