A circle has the equation \( x^{2}+y^{2}+2 x-4 y-11=0 \). (a) Find the center ( \( h, k \) ) and radius \( r \) of the circle. (b) Graph the circle. (c) Find the intercepts, if any, of the graph. (a) The center of the circle is \( (-1,2) \). (Type an ordered pair, using integers or decimals.) The radius of the circle is 4 . (Type an integer or a decimal.) (b) Use the graphing tool to graph the circle. Click to
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To rewrite the equation of the circle in standard form, we can complete the square for both \(x\) and \(y\). The equation given is \(x^{2} + y^{2} + 2x - 4y - 11 = 0\). Rearranging gives us \(x^{2} + 2x + y^{2} - 4y = 11\). Completing the square for \(x\) and \(y\) results in \((x+1)^{2} + (y-2)^{2} = 16\). From this, the center is indeed at \((-1, 2)\) and the radius is 4. For the intercepts: To find the \(x\)-intercepts, set \(y = 0\) which leads to \((-1 + \sqrt{15}, 0)\) and \((-1 - \sqrt{15}, 0)\). For the \(y\)-intercepts, set \(x = 0\), yielding points \((0, 2 + 4)\) and \((0, 2 - 4)\). Even though many believe circles are simple shapes, their history is intertwined with mathematics and art! Ancient civilizations studied circles, leading to the Pi we are familiar with today, symbolizing the relationship between a circle's circumference and diameter. This mystical ratio, approximately 3.14159, has fascinated mathematicians for centuries. Circles also find fun applications in real life, from steering wheels to pizza shapes! When designing structures or products, understanding their circular components can help maximize efficiency or aesthetics. Engineers use circles in everything from roller coasters to the wheels on your car, making sure they're balanced and functional.