Question

What is the radius of a circle given by the equation x2 + y2 – 2x + 8y – 47= 0? radius = units

Answer 1

Answer:

8 units

Step-by-step explanation:

We need to rewrite an equation in the standard for  a circle form.

r is radius.

(x−h)²+(y−k)²= r²

x² + y² – 2x + 8y – 47= 0

x² - 2x + y² + 8y - 47 = 0

x² - 2*x *1+ 1 ²- 1² + y² + 2*4*y + 4² - 4² - 47 = 0

(x - 1)² + (y + 4)² - 1 - 16 -47 =0

(x - 1)² + (y + 4)² - 64=0

(x - 1)² + (y + 4)² = 8²

Radius is 8.

Answer 2

The radius of the circle is 8 units

What is radius?

The radius of a circle is a line drawn from the center to the circumference of the circle

The equation of the circle is given as;

$x^2 + y^2 - 2x + 8y - 47 = 0$

Rewrite the equation as:

$x^2 - 2x + y^2 + 8y = 47$

Next, we rewrite the equation in the standard form

So, we have:

x^2 - 2x + 1^2 - 1^2 + y^2 + 8y + 4^2 - 4^2 = 47

Evaluate the exponents

x^2 - 2x + 1 - 1 + y^2 + 8y + 16 - 16 = 47

Rewrite the equation as follows:

x^2 - 2x + 1 + y^2 + 8y + 16 = 47 + 1 + 16

Express as perfect squares

(x - 1)² + (y + 4)² = 64

(x - 1)² + (y + 4)² = 8^2

The radius of the circle is calculated as:

r^2 = 8^2

By comparison, we have:

r = 8

Hence, the radius of the circle is 8 units

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