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( with solution )
Activity 2: Write the following equations of a circle to center-radius form.
1. x2 - 6x + y2 + 8y + 5 = 0
2. x2 + y2 + 6x - 8y + 5 = 0
3. x2 + y2 - 4x + 2y + 4 = 0
4. x2 + y2 + 2x - 6y = - 14
5. x2 + y2 + 3x + 5y + 9/4 = 0


Sagot :

1)

x² - 6x + y² + 8y + 5 = 0

(x² - 6x) + (y² + 8y) = - 5

(x² - 6x + 9) + (y² + 8y + 16) = - 5 + 9 + 16

(x - 3)² + (y + 4)² = (2√5)²

Center: (3,- 4) ; Radius: 2√5

2)

x² + y² + 6x - 8y + 5 = 0

(x² + 6x) + (y² - 8y) = - 5

(x² + 6x + 9) + (y² - 8y + 16) = - 5 + 9 + 16

(x + 3)² + (y - 4)² = (25)²

Center: ( - 3,4) ; Radius: 2√5