About Graphing Circles:
In some cases, we will need to find the equation of a circle in center-radius form, otherwise known as standard form. Additionally, we may need to use the equation of a circle in center-radius form to graph circles on the coordinate plane.
Test Objectives
- Demonstrate the ability to write the equation of a circle in standard form
- Demonstrate the ability to write the equation of a circle in general form
- Demonstrate the ability to graph a circle
#1:
Instructions: find the center-radius form.
$$a)\hspace{.2em}x^2 + y^2 + 12x - 2y + 12=0$$
$$b)\hspace{.2em}x^2 + y^2 - 28x - 14y + 236=0$$
$$c)\hspace{.2em}x^2 + y^2 - 4x - 14y + 4=0$$
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#2:
Instructions: write each equation in general form.
$$a)\hspace{.2em}(x - 16)^2 + (y - 11)^2=9$$
$$b)\hspace{.2em}(x + 8)^2 + (y - 3)^2=44$$
$$c)\hspace{.2em}(x + 10)^2 + (y - 9)^2=49$$
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#3:
Instructions: find the x and y intercepts.
$$a)\hspace{.2em}x^2 + y^2=49$$
$$b)\hspace{.2em}x^2 + y^2 + 30x + 22y + 342=0$$
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#4:
Instructions: graph each circle.
$$a)\hspace{.2em}x^2 + y^2 + 6x + 8y + 21=0$$
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#5:
Instructions: graph each circle.
$$a)\hspace{.2em}x^2 + y^2 - 2x + 6y + 1=0$$
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Written Solutions:
#1:
Solutions:
$$a)\hspace{.2em}(x + 6)^2 + (y - 1)^2=25$$
$$b)\hspace{.2em}(x - 14)^2 + (y - 7)^2=9$$
$$c)\hspace{.2em}(x - 2)^2 + (y - 7)^2=49$$
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#2:
Solutions:
$$a)\hspace{.2em}x^2 + y^2 -32x - 22y + 368=0$$
$$b)\hspace{.2em}x^2 + y^2 + 16x - 6y + 29=0$$
$$c)\hspace{.2em}x^2 + y^2 + 20x - 18y + 132=0$$
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#3:
Solutions:
$$a)\hspace{.2em}$$ $$x\text{-intercepts} : (7,0), (-7,0) $$ $$y\text{-intercepts}: (0,7), (0,-7)$$
$$b)\hspace{.2em}$$ $$x\text{-intercepts} : \text{none}$$ $$y\text{-intercepts}: \text{none}$$
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#4:
Solutions:
a)
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#5:
Solutions:
a)