Answer: 
Step-by-step explanation:
We know that the standard quadratic equation is ax^2+bx+c=0
Let's compare all the given equation to it and , find discriminant.
1. a=2, b= -7, c=-9
So it has 2 real number solutions.
2. a=1, b=-4, c=4

So it has only 1 real number solution.
3. a=4, b=-3, c=-1

So it has 2 real number solutions.
4. a=1, b=-2, c=-8
So it has 2 real number solutions.
5. a=3, b=5, c=3

Thus it does not has real solutions.
9514 1404 393
Answer:
8.6
Step-by-step explanation:
The growth factor per year is 1.012, so in 500 years is ...
1.012^500
The number of doublings is the solution to ...
2^n = 1.012^500
Taking logarithms, we have ...
n·log(2) = 500·log(1.012)
n = 500·log(1.012)/log(2) ≈ 8.6046
About 8.6 doublings will take place in 500 years.
Answer:
$20.60
Step-by-step explanation:
25.75x20%=5.15
25.75-5.15=20.60