Answer:
A is your answer
Step-by-step explanation:
Is C and D because 10x^2-6x^2=36+64
4x^2=100
x^2=25
x= -5 or 5
So, h(t) is how far is Daniel's head from the surface of the water, namely the surface itself is when the height is nill, so his head is at the surface and the height of it is just 0, thus h(t) = 0. Namely, what is "t" when h(t) is 0?

clearly the seconds cannot be a negative unit, so is not -3/2.
Answer:
x = 0
, y = 7/6
Step-by-step explanation:
Solve the following system:
{18 y - 12 x = 21
6 x - 9 = -9
In the second equation, look to solve for x:
{18 y - 12 x = 21
6 x - 9 = -9
Add 9 to both sides:
{18 y - 12 x = 21
6 x = 0
Divide both sides by 6:
{18 y - 12 x = 21
x = 0
Substitute x = 0 into the first equation:
{18 y = 21
x = 0
In the first equation, look to solve for y:
{18 y = 21
x = 0
Divide both sides by 18:
{y = 7/6
x = 0
Collect results in alphabetical order:
Answer: {x = 0
, y = 7/6