Answer:
Step-by-step explanation:
-5x² - 6 = -4x
-5x² + 4x - 6 = 0
a = -5 ; b = 4 ; c = -6
Discriminant = b² - 4ac
= 4² - 4*(-5)*(-6)
= 16 - 120
= -104
roots = 
![=\dfrac{-4+\sqrt{-104}}{2*(-5)};\dfrac{-4-\sqrt{-104}}{2*(-5)}\\\\=\dfrac{-4+2i\sqrt{26}}{-10} ; \dfrac{-4-2i\sqrt{26}}{-10}\\\\=\dfrac{(-2)[2-i\sqrt{26}]}{-10} \ ; \ \dfrac{(-2)[2+i\sqrt{26}]}{-10}\\\\=\dfrac{2-i\sqrt{26}}{5} \ ; \ \dfrac{2+i\sqrt{26}}{5}](https://tex.z-dn.net/?f=%3D%5Cdfrac%7B-4%2B%5Csqrt%7B-104%7D%7D%7B2%2A%28-5%29%7D%3B%5Cdfrac%7B-4-%5Csqrt%7B-104%7D%7D%7B2%2A%28-5%29%7D%5C%5C%5C%5C%3D%5Cdfrac%7B-4%2B2i%5Csqrt%7B26%7D%7D%7B-10%7D%20%3B%20%5Cdfrac%7B-4-2i%5Csqrt%7B26%7D%7D%7B-10%7D%5C%5C%5C%5C%3D%5Cdfrac%7B%28-2%29%5B2-i%5Csqrt%7B26%7D%5D%7D%7B-10%7D%20%5C%20%3B%20%5C%20%5Cdfrac%7B%28-2%29%5B2%2Bi%5Csqrt%7B26%7D%5D%7D%7B-10%7D%5C%5C%5C%5C%3D%5Cdfrac%7B2-i%5Csqrt%7B26%7D%7D%7B5%7D%20%5C%20%3B%20%5C%20%5Cdfrac%7B2%2Bi%5Csqrt%7B26%7D%7D%7B5%7D)
The percentage of the radioactive isotope left is 25.0000%.
<h3>What is the half life?</h3>
The half life of a radioactive isotope is the time that will elapse before only half of the number of original isotopes will remain.
Now;
We are told that;
Half life (t1/2) = 55 days
Time taken (t) = 115 days
Ratio of isotope remaining = N/No
Thus;
N/No = (1/2)^t/t1/2
N/No = (1/2)^115/55
N/No = (1/2)^2
N/No =1/4
Hence, the percentage = 1/4 * 100/1 = 25.0000%
Learn more about half life of an isotope:brainly.com/question/16387602
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You write 10+4+.05.
this is because you add each value separately <span />
Answer: A 729
Step-by-step explanation: