Number of ways the first 4 databases can be selected = 9C4 = 126
Probability that it is in 2 of the first 4 = 5C2 / 126 = 10/126
Probability that it is in 3 of the first 4 = 5C3 / 126 = 10/126
Probability that it is in 4 of the first 4 = 5C4 / 126 = 5/126

Probability that it is in at least 2 of the first 4 = 10/126 + 10/126 + 5/126 = 25/126

5 0

3 years ago

The general form of the equation of a circle is x2 + y2 + 42x + 38y − 47 = 0. The equation of this circle in standard form is A)

jolli1 [7]

The common way of transforming the general form to the standard form is by using the completing the square method. But there is also a neat shortcut to knowing the h, k and r values right away.
The general formula is:
x²+y²+Dx+Ey+F = 0
x² + y² + (-2h)x + (-2k)y + (h²+k²-r²) = 0

Solving for h:
-2h = 42
h = -21

Solving for k:
-2k = 38
k = -19

Solving for r:
-47 = (-21)² + (-19)² - r²
r = √849

Standard form of given circle is:
(x+21)² + (y+19)² = 849

Answers:
1) B
2) B
3) B
4) D

4 0

2 years ago