Find the centre and radius of the circle x2 + y2 – 2x + 4y = 8 – InterviewSolution

1.

Find the centre and radius of the circle x2 + y2 – 2x + 4y = 8

Answer»

we write the given equation in the form (x² – 2x) + ( y² + 4y) = 8

Now, completing the squares, we get

(x² – 2x + 1) + ( y₂ + 4y + 4) = 8 + 1 + 4

(x – 1)² + (y + 2)² = 13

Comparing it with the standard form of the equation of the circle, we see that the centre of the circle is (1, –2) and radius is √13

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