Well first, we must remember the formula for the area of a circle.
The formula for the area of a circle is:
PiR^2, or Pi • R^2.
Basically this means 3.14 (Pi) • R • R (Radius).
We have our radius, 4, so we can plug in our numbers to solve.
3.14 • 4 • 4 is our formula, so let's solve.
4 • 4 = 16.
16 • 3.14 = 50.24.
Remember when we solve for the area, we use units squared (units^2).
Your answer is 50.24 cm^2.
I hope this helps!
Answer:
x=-(7
)
Step-by-step explanation:
It isn't at all!
When dividing numbers, the easiest way is to imagine the values as a fraction, and then reduce that fraction. If it reduces to a core fraction (ones that you should know their decimal value without thinking), then you have your answer.

We simplified our fraction by dividing the numerator and denominator by 4, which left us with

, which we know is equal to
0.8.
You may be confused thinking that 0.8 is the same as 8. 0.8 is actually a tenth of the value of 8. This makes them very different values.
Below, I have also included a picture to help you memorize your common/core fractions. I recommend learning these as they will help you get through all sorts of math, from Geometry to Calculus!
Step-by-step explanation:
1. The equation graph is a parabola, so the maximum height will be the vertex of the parabola. You can find the vertex coordinate t using the formula:
t = -b/2a
t = -18/2•(-4.9)
t = -18/-9.8
t = 1.84 seconds
2. The height of the ground is 0, so the balls hit the ground when the equation result is 0:
0 = -4.9t²+18t+10
Now you solve it using Bhaskara:
Δ = b² -4ac
Δ = 18² -4•(-4.9)•10
Δ = 520
t = (-b ±√Δ)/2a
t = (-18 ± √520)/2•(-4.9)
t1 = (-18 - 20.8)/-9.8
t1 = 3.96 seconds
t2 = (-18 +20.8)/-9.8
t2 = -0.28
Doesn't exist negative time, so we pick the first value found, t = 3.96 seconds
3. Now you just need to put 3 in place of t to find the result:
h = -4.9•3² +18•3 +10
h = -4.9•9 + 54 + 10
h = -44.1 + 64
h = 19.9 meters
4. You just need to put 1 in place of t to find the height:
h = -4.9•1²+12
h = -4.9+12
h = 7.1 meters