First, fint the roots of the equation 
1.
2. You can see that this equation has two different real roots. Note that you can make this statement without finding roots, only knowing the value of discriminant: since D=81>0, then the equation has two different real roots.
Answer:
The length is 0.83
Step-by-step explanation:
<span>60.5 milligrams per square centimeter
First, determine how many half lives have expired by dividing the time by the half-life. So:
55/20 = 2.75
That means that only 2^(-2.75) = 0.148650889 = 14.8650889% of the original substance remains. So just divide the amount remaining by 0.148650889 to get the original amount.
9 / 0.148650889 = 60.5445419
So originally, there was 60.5 milligrams per square centimeter 55 years ago.</span>
