Answer:
We know that the equation of the circle in standard form is equal to <em>(x-h)² + (y-k)² = r²</em> where (h,k) is the center of the circle and r is the radius of the circle.
We have x² + y² + 8x + 22y + 37 = 0, let's get to the standard form :
1 - We first group terms with the same variable :
(x²+8x) + (y²+22y) + 37 = 0
2 - We then move the constant to the opposite side of the equation (don't forget to change the sign !)
(x²+8x) + (y²+22y) = - 37
3 - Do you recall the quadratic identities ? (a+b)² = a² + 2ab + b². Now that's what we are trying to find. We call this process <u><em>"completing the square"</em></u>.
x²+8x = (x²+8x + 4²) - 4² = (x+4)² - 4²
y²+22y = (y²+22y+11²)-11² = (y+11)²-11²
4 - We plug the new values inside our equation :
(x+4)² - 4² + (y+22)² - 11² = -37
(x+4)² + (y+22)² = -37+4²+11²
(x+4)²+(y+22)² = 100
5 - We re-write in standard form :
(x-(-4)²)² + (y - (-22))² = 10²
And now it is easy to identify h and k, h = -4 and k = - 22 and the radius r equal 10. You can now complete the sentence :)
X+x+3x= 180
5x= 180
x= 36
3(36)= 108
Your answer is D. $108
Answer:
r = - 7, r = - 5
Step-by-step explanation:
Given
r² = - 12r - 35 ( add 12r to both sides )
r² + 12r = - 35
To complete the square
add ( half the coefficient of the r- term )² to both sides
r² + 2(6)r + 36 = - 35 + 36
(r + 6)² = 1 ← take the square root of both sides )
r + 6 = ± 1 ( subtract 6 from both sides )
r = - 6 ± 1, thus
r = - 6 - 1 = - 7 or r = - 6 + 1 = - 5
