Question

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53 & 54. State the center and radius of circle. Then graph the circle below ​

Answer 1

General equation of circle

• (x-h)²+(y-k)²=r²

centre(h,k)

radius=r

#53

• (x-3)²+(y+4)²=16

Centre (3,-4)

radius=√16=4units

#54

• (x+2)²+(y+0)²=50

Centre(-2,0)

Radius=√50units

Answer 2

Equation of a circle

`(x-a)^2+(y-b)^2=r^2`

where:

• (a, b) is the center
• r is the radius

Question 53

Given equation:
`(x-3)^2+(y+4)^2=16`

Comparing this with the general equation of a circle:

⇒ center = (3, -4)

⇒ radius = √16 = 4

Question 54

Given equation:
`(x+2)^2+y^2=50`

Comparing this with the general equation of a circle:

⇒ center = (-2, 0)

⇒ radius = √50 = 5√2 = 7.1 (1 dp)

To graph the circles:

• Plot the center point.
• Set your compass to the width of the radius.
• Place the sharp point on the center point and draw the circle.

(Graphs attached)