I would add, the weight of the backpack and the weight of the school books which is 28.36.
So Rico's backpack altogether weighs 28.36.
I'm pretty sure.
The critical points of a function are the values of x, for which the function is equal to zero.
Given the inequality
A rational function is said to be equal to zero when the numerator is equal to zero.
Thus
Therefore, the critical point of the inequality is x = -2 and x = 2.
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
The answer to your question is:
It is a quadratic equation in 'x', with 'n' mistakenly typed in the second term..
Although you didn't ask for the solutions to the equation, I'm already here
so I might as well go through it and find them:
<span><u>3x² - 2x - 5 = 0</u></span>
In terms of the generic quadratic formula:
A = 3
B = -2
C = -5
Plug those into the quadratic formula, and you discover that
<u>x = -1</u>
and
<u>x = ⁵/₃</u>