A firecracker is shot upward off a balcony that is 10 feet above the ground with an initial velocity of v feet per second. The firecracker reaches a maximum height of 30.25 feet at 1.125 seconds after being shot upward. The formula for the vertical motion of an object is
where the gravitational constant, a, is -32 feet per second, and h(t) is the height in feet modeled as a function of time, t.

The initial velocity of the firecracker is
A. 12
B. 27
C. 36
feet per second

The time when the firecracker reaches the ground is
A. 1.25
B. 2
C. 2.5
seconds

The correct answers are C and C I just need to understand why.
Thanks!

The rate of decay of a radioactive substance depends upon the amount present initially. the mass y (mg) of the radioactive substance cobalt-60 present in a sample at time t (years) is represented by the exponential equation y=50e −0.1315 t . answer the following questions in complete sentences. 1. how does the exponential equation above compare to the equation for simple interest that is compounded continuously? explain the similarities. 2. what is the initial amount of cobalt-60 in the sample? 2. how much cobalt-60 is left after 8.4 years? show your work. 3. what would be the y-intercept of the graph? what does it represent? 4. after how many years will the amount of cobalt-60 left be 6.25 mg? explain what happens to the cobalt-60 after 50 years? 5. discuss some “real-world” examples and uses of cobalt-60

Which expression is equivalent to -5(3x - 6/7)

For problems 29 - 31 the graph of a quadratic function y=ax^2 + bx + c is shown. tell whether the discriminant of ax^2 + bx + c = 0 is positive, negative, or zero.