Question

I have a question, can anybody help me?

What is the general form of the equation of the given circle with center A?


http://cdn.ple.platoweb.com/PCAP-ASSETS-PROD/258cc385d685420384bc0a8b50aa8568

x2 + y2 + 6x − 24y − 25 = 0

x2 + y2 − 6x + 24y + 128 = 0

x2 + y2 + 6x – 24y + 128 = 0

x2 + y2 + 6x − 24y + 148 = 0

Answer 1

The equation of a circle with the center (h, k) and radius r is
\[(x-h)^2+(y-k)^2=r^2\]
Your center is (-3,12) so that's h and k. Your radius is 5. Plug in the numbers and expand the equation

Answer 2

(x-(-3)2 + (y-12)2 = 25 right?

Answer 3

yes

Answer 4

and what do i do next ? :s

Answer 5

foil (x+3)² and (y-12)²

Answer 6

is it (x+9) + (y + 144) = 25 ??

Answer 7

no. you need to use FOIL for both the x and y
(x + 3)² + (y - 12)² = 25
means
\[(x+3)(x+3)+(y-12)(y-12)=25\]

Answer 8

so it would be 6x and 24y right?

Answer 9

6x and -24y

Answer 10

okay so we can take out b and c in the answers right?

Answer 11

yes

Answer 12

is it a?

Answer 13

i don't know. I'm not actually working this problem. just following along to make sure your work is right. and now that I look it doesn't look like you can exclude both b and c yet

Answer 14

Ugh, i suck at math x.x

Answer 15

what did you get when you multiplied (x+3)(x+3)?
you've got to show me something so I can see where you're going wrong

Answer 16

6x and -24y

Answer 17

you couldn't have gotten just 6x and -24y. Show me the whole equation

Answer 18

once we got that part right I can show you how to simplify it into the form they want

Answer 19

so this is what I got with FOIL
(x-3) + (x-3) + (y-12) + (y-12) = 25

Answer 20

not sure if you have to multiply the 25 too..

Answer 21

ok. so FOIL is actually multiplication. it stands for First, Inner, Outer, Last. just to help you remember how to distribute. I'm going to show you (x - 3)(x - 3).