Answer:
The pebble will hit the ground 8.29 second after it is thrown.
Step-by-step explanation:
Given that,
The height of the pebble after t seconds is given by the equation
h= -16t²+24 t+900.
When the pebble hit the ground, the height of the pebble will be zero.
So putting h=0 in the given equation.
0 = -16t²+24 t+900
⇒-4(4t²-6t-225)=0
⇒4t²-6t-225=0
Applying quadratic formula
, here a=4, b= -6 and c= -225.

⇒ t = 8.29, -6.79
Since time can not negative.
∴t=8.29 seconds.
The pebble will hit the ground 8.29 second after it is thrown.
A constant of variation is only in the form ay=bx where b/a=constant so given any point y/x=constant let us check here by substituting x=1 and x=2
when x=1---> 2y=14,y=7 here y/x=7
when x=2--->2y=19,y=9.5 here y/x=4.75
so this equation is not constant of variation
let us check an equation of the form 3y=7x
when x=1--->y=7/3--->y/x=7/3
when x=2--->y=14/3---->y/x=7/3
so 3y=7x is a constant of variation
C. Table T
It is not a function if one x value gives more than 1 y-value. In table T, 3 gives 4 and -4 two different y values.