I need help, please and thank you. I know that you have to multiply the diameter by 2 to find the radius, but with the 9 pi, it makes me unsure if I'm doing this correctly.

r=6

Step-by-step explanation:

The area of a circle is given by πr². Note that this uses the radius, not the diameter.

Now, one quarter of this area (ABC) is given to be 9π.

So apparently:

If you solve this:

(divide both sides by π)

(multiply both sides by 4)

so

r = √36 = 6

so the radius is 6.

answer: b.

step-by-step explanation:

the y coordinate for point b is 0, and answer b is the only one with that y coordinate.

the solution of the equation is 2.23 ⇒ answer b

step-by-step explanation:

* lets revise the meaning of exponential function

- the form of the exponential function is y = ab^x, where a ≠ 0, b > 0 ,  

  b ≠ 1, and x is any real number

- it has a constant base b

- it has a variable exponent x

- to solve an exponential equation, take the log or ln of both sides,  

  and solve for the variable

* lets solve the problem

∵

- the base is 7 and the exponent is x

- insert ㏑ in both sides

∴

- use the rule

∴ x ㏑(7) = ㏑(77)

- to find x divide both sides by ㏑(7)

∴

* the solution of the equation is 2.23 to the nearest 2 decimal places