Which of the following circles lie completely within the fourth quadrant? check all that apply. a. (x-12)^2 + (y+0)^2= 72 b. (x-2)^2 + (y+7)^2= 64 c. (x-9)^9 + (y+9)^2= 16 d. (x-9)^2 + (y+5)^2= 9

C. (X-9)^9 + (y+9)^2= 16

D. (X-9)^2 + (y+5)^2= 9

Step-by-step explanation:

The formula for a circle is

(X-h)^2 + (y-k)^2= r^2

where (h,k) is the center of the circle and r is the radius

The 4th quadrant is where x is positive and y is negative

Add r to the y coordinate of the center and if it is still negative, the circle is still completely in the 4th quadrant

A. (X-12)^2 + (y+0)^2= 72

The center is at 12,0 and the radius is sqrt(72) = 6sqrt(2)

This will be positive so it goes into the 1st quadrant

B. (X-2)^2 + (y+7)^2= 64

The center is at 2,-7  and the radius is 8

-7+8=1 so it goes into the 1st quadrant

C. (X-9)^9 + (y+9)^2= 16

The center is at 9,-9  and the radius is 4

-9+4 = -5  so it is completely in the 4th quadrant

D. (X-9)^2 + (y+5)^2= 9

The center is at 9,-5 and the radius is 3

-5+3 = -2 so it is completely in the 4th quadrant

C and D

Step-by-step explanation:

The fourth quadrant is the bottom, right quadrant. In the fourth quadrant, the x-coordinate is positive, and the y-coordinate is negative.

For a circle to be completely within the fourth quadrant, the circle must have its center in the fourth quadrant, and the center has to be far away enough from the positive x-axis and from the negative y-axis, that no points on the circle are outside the fourth quadrant.

Choice A has center (12, 0), so it cannot be.

Choice B has center (2, -7) and radius 8. Many points will be past the axes.

Choice C has center (9, -9) and radius 4. All points will be in the fourth quadrant.

Choice D has center (9, -5) and radius 3. All points will be in the fourth quadrant.

ending amount = beginning amount / (2^n)

where "n" = number of half-lives (or elapsed time / half-life)

ending amount = 50 mg / (2 ^10 / 5.3)

ending amount = 50 mg / (2 ^ 1.8867924528)

ending amount = 50 m / 3.6981210597

ending amount = 13.5203794557 mg

or about 13.5 mg remain

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