Answer:

Step-by-step explanation:
For the function to have a domain of all reals, the denominator cannot have a value of zero. x^2 + 2cx + 14 will not have zero as a root if it has no real solutions. A quadratic equation has no solutions when the discriminant is negative.
b^2 - 4ac < 0
(2c)^2 - 4(1)(14) < 0
4c^2 - 56 < 0
4c^2 < 56
c^2 < 14

If I=P*r*t, we can input 450 in for I, 3000 in for the principal (P, or the starting rate), and 3 for t=time because there were three years, resulting in 450=9000*r. Next, we can divide both sides by 9000 to get 0.05 or 5% as our answer.