AM-2342

Equation of a circle (general form)

A Math · Secondary 4 · Medium · Equation of a circle (general form)

A circle has equation

x^2 + y^2 - 4x + 8y = 5

. What is its centre and radius?

Centre $(2,-4)$ , radius $5$
Centre $(-2,4)$ , radius $5$
Centre $(2,-4)$ , radius $\sqrt{5}$
Centre $(-2,-4)$ , radius $5$

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