Answer:
First option: 
Second option: 
Fourth option: 
Step-by-step explanation:
Rewrite each equation in the form
and then use the Discriminant formula for each equation. This is:

1) For
:

Then:
Since
this equation has no real solutions, but has two complex solutions.
2) For
:

Then:
Since
this equation has no real solutions, but has two complex solutions.
3) For
:

Then:
Since
this equation has one real solution.
4) For
:
Then:
Since
, this equation has no real solutions, but has two complex solutions.
To solve for y, isolate the variable to one side.
9x+3y=4
-9x -9x
~~~~~~~~
3y= -9x+4
~~~~~~~~
3y= -9x+4 (Divide both sides by 3)
y=-3x+4
Answer:
y = 5 e^r * t
Let y be the population in billions and t the value of elapsed years
7 = 5 e^r * t is the equation being used where t = 15
7/5 = e^r * t
ln 7/5 = r * t taking ln of both sides
r = .336 / 15 = .0224
y = 5 e^(.0224 t) is then our equation
Check - suppose you want y at 2020
y = 5 e^(.0224 * 20) would be the equation
y = 5 e^.449 = 7.83 billion - seems to be a reasonable answer
4.8541019662497 + 1.8541019662497 = -3
<span>-4.8541019662497 x 1.8541019662497 = -9</span>
(9-243)/(4-1)=-78
D)−78 contestants per round, and it represents the average rate at which the number of contestants changed from the first round to the fourth roundReport · <span>14/12/2015</span>