Since absolute value is just taking the positive value of whatever you put in the function, it is 7.8 as well. Also, absolute value can be described as the distance from 0 on the number line. 7.8 is 7.8 "units" away from 0, thus meaning it is equal to 7.8.
From the equation of motion, we know,

Where s= displacement
u= initial velocity
a= gravitational force
t= time
Displacement is 0 since the ball comes back to the same point from where it was thrown.
A =
since the ball is thrown upwards.
Plug the known values into the equation.
=> 
Solving for u gives :
u= 16.67 m/ sec ....... equation (1)
At maximum height, final velocity i.e v is 0
Time take to reach the top = 

=> 
Solving for s we get
s= 14.16 m
X^3-7x^2-5x+35
= x^2(x-7) - 5 (x-7) now by definition
=(x^2-5)(x-7)
hope this helps