Answer:
-14.2
Step-by-step explanation:
Let's say this number is a:
a*(a-9) = 90
a^2-9a-90 = 0
(a-15)(a+6) = 0
a = 15 or a = -6
Therefor a. would be the correct answer :)
The equation form of a circle is (x - a)² + (y - b)² = r²
Equation 1:
x² - 4x + y² + 12y - 20 = 0 ⇒ use the completing the square method for x² - 4x and y² + 12y
x² - 4x = (x - 2)² - 4
y² + 12y = (y + 6)² - 36
Put them back together, we have
(x - 2)² - 4 + (y + 6)² - 36 - 20 = 0
(x - 2)² + (y + 6)² -4 - 36 - 20 = 0
(x - 2)² + (y + 6)² - 60 = 0
(x - 2)² + (y + 6)² = 60
Equation 2:
x² + y² + 6x - 8y - 10 = 0
(x² + 6x) + (y² - 8y) -10 = 0
(x + 3)² - 9 + (y - 4)² -16 - 10 = 0
(x + 3)² + (y - 4)² - 9 - 16 - 10 = 0
(x + 3)² + (y - 4)² - 35 = 0
(x + 3)² + (y - 4)² = 35
Equation 3:
3x² + 12x + 3y² +18y - 15 = 0
3 [x² + 4x + y² + 6y - 5] = 0
x² + 4x + y² + 6y - 5 = 0
(x² + 4x) + (y² + 6y) - 5 = 0
(x + 2)² - 4 + (y + 3)² - 9 - 5 = 0
(x + 2)² + (y + 3)² - 4 - 9 -5 = 0
(x + 2)² + (y + 3)² - 18 = 0
(x + 2)² + (y + 3)² = 18
Equation 4:
5x² + 5y² - 10x + 20y - 30 = 0
5 [x² + y² - 2x + 4y - 6] = 0
x² + y² - 2x + 4y - 6 = 0
(x² - 2x) + (y² + 4y) - 6 = 0
(x - 1)² - 2 + (y + 2)² - 4 - 6 =0
(x - 1)² + (y + 2)² - 2 - 4 - 6 = 0
(x - 1)² + (y + 2)² - 12 = 0
(x - 1)² + (y + 2)² = 12
Equation 5:
2x² + 2y² - 24x - 16y -8 = 0
2 [x² + y² - 12x - 8y - 4] = 0
x² + y² - 12x - 8y - 4 = 0
(x² - 12x) + (y² - 8y) - 4 = 0
(x - 6)² - 36 + (y - 4)² - 16 - 4 = 0
(x - 6)² + (y - 4)² -36 - 16 - 4 = 0
(x - 6)² + (y - 4)² - 56 = 0
(x - 6)² + (y - 4)² = 56
Equation 6:
x² + y² + 2x - 12y - 9 = 0
(x² + 2x) + (y² - 12y) - 9 = 0
(x + 1)² - 1 + (y - 6)² - 36 - 9 = 0
(x + 1)² + (y - 6)² - 1 - 36 - 9 = 0
(x + 1)² + (y - 6)² - 46 = 0
(x + 1)² + (y - 6)² = 46
