What is the radius of a circle whose equation is x² + y² + 8x – 6y + 21 = 0?

units

The radius of circle whose equation is is 2 units.

Step-by-step explanation:

Given equation of  a circle is

We have to find the radius of the circle whose equation is given.

Consider the given equation of  a circle is

General equation of circle having center at (h,k)  with radius r is given as ,

........(1)

we first write the given equation in the general form by making perfect squares,

We know

For making perfect square of x, we have terms, we just need

On comparing w have b = 4 , thus

So adding both side 16 , equation becomes,

For making perfect square of y, we have terms, we just need

On comparing w have b = 3 , thus

So adding both side 9 , above equation becomes,

On solving, we get,

.....(2)

Comparing (1) and (2) , we have  r= 2

Thus, the radius of circle whose equation is is 2 units.

5=812a+9+3

step 1: simplify both sides of the equation.

5=812a+9+3

5=(812a)+(9+3)(combine like terms)

5=812a+12

5=812a+12

step 2: flip the equation.

812a+12=5

step 3: subtract 12 from both sides.

812a+12−12=5−12

812a=−7

step 4: divide both sides by 812.

812a /812 = -7/812

a= -1/116

so the answer is

a=   -1/116