It would be subtraction I think
The given equation of parabola is

Which can also be written as

Here vertex (h,k) is (1,2)
And value of a is

Formula of focus is

Substituting the values of h,k and a, we will get

Therefore the correct option is the last option .
Answer: 8 feet below sea level is higher
Step-by-step explanation:
<h3>The first time when the ball will reach a height of 20 feet is 0.42 seconds</h3>
<em><u>Solution:</u></em>
Given that,
<em><u>The height of a ball thrown into the air after t seconds have elapsed is:</u></em>

<em><u>What is the first time, t, when the ball will reach a height of 20 feet?</u></em>
Substitute h = 20

<em><u>Solve by quadractic formula</u></em>




Rounding off we get,
t = 2.08 , t = 0.42
Thus the first time when the ball will reach a height of 20 feet is 0.42 seconds