Sabemos que :
<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" />
Por lo que remplazamos :
<img src="https://tex.z-dn.net/?f=d%3D%5Cfrac%7B-20%2B%5Csqrt%7B20%5E2-4%5Cleft%28-42%5Cright%292%7D%7D%7B2%5Ccdot%20%5C%3A2%7D%3D%5Cfrac%7B1%7D%7B4%7D%5Cleft%284%5Ccdot%20%5Csqrt%7B46%7D-20%5Cright%29%3D%5Csqrt%7B46%7D-5" />
y
<img src="https://tex.z-dn.net/?f=d%3D%5Cfrac%7B-20-%5Csqrt%7B20%5E2-4%5Cleft%28-42%5Cright%292%7D%7D%7B2%5Ccdot%20%5C%3A2%7D%3D%5Cfrac%7B1%7D%7B4%7D%5Cleft%28-20-4%5Ccdot%20%5Csqrt%7B46%7D%5Cright%29%3D-5-%5Csqrt%7B46%7D" />
Por lo que :
<img src="https://tex.z-dn.net/?f=d%3D%5Csqrt%7B46%7D-5%2C%5C%3Ad%3D-5-%5Csqrt%7B46%7D" />
En decimal :
x = - 11, 7823 y x = 1, 7823.