Find the area of the circle whose equation is given as \(x^{2} + y^{2} - 4x + 8y + 11 = 0\).

Assessment: WAEC SSCE - Further Mathematics - 2007 (Objective) Subject: Further Mathematics

Question 1 Report

Find the area of the circle whose equation is given as \(x^{2} + y^{2} - 4x + 8y + 11 = 0\).

Answer Details
To find the area of the circle whose equation is given as \(x^{2} + y^{2} - 4x + 8y + 11 = 0\), we need to first complete the square for both \(x\) and \(y\). Rearranging the equation, we get: \begin{aligned} x^2 - 4x + y^2 + 8y &= -11 \\ x^2 - 4x + 4 + y^2 + 8y + 16 &= 9 \\ (x-2)^2 + (y+4)^2 &= 3^2 \end{aligned} Now we can see that the equation represents a circle with center \((2, -4)\) and radius \(3\). The formula for the area of a circle is \(A = \pi r^2\), where \(r\) is the radius. In this case, the radius is \(3\), so the area is: \begin{aligned} A &= \pi r^2 \\ &= \pi (3)^2 \\ &= \boxed{9\pi} \end{aligned} Therefore, the answer is \(\boxed{9\pi}\).

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