Answer:
F = M a is the vector equation involved
F = T - M g are the forces acting on the elevator (scalar equation)
T - M g = M a
T = M (a + g) remember this a scalar
If a is slowing down then it must have a positive acceleration upwards
Therefor the tension in the cable must be greater than zero
When the tension increases to M g, a has increased to zero
For a to be zero, no acceleration, T = M g
The root quadratic equation of
is 
What is the formula used to calculate the quadratic equation?
To solve the quadratic equation use the formula of 
Find the quadratic equation by using the formula ?
On comparing with 
We get , 

By using the formula,
For a quadratic equation of the form
the solutions are


Apply rule,

Apply exponent rule,
if n is even


Multiply the numbers :

Add the number 
Answer:
A figure skater doing a double axle
The swing of a baseball bat
The leverage on a hockey stick
hope it helps