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anonymous

  • one year ago

What is the equation of the circle with center (2,-5) that passes through the point (-2,10)? a. (x-2)^2+(y-(-5))^2=25 b. (x-(-2))^2+(y-10)^2=241 c. (x-2)^2+(y-(-5))^2=241 d. (x-(-2))^2+(y-10)^2=25 I'm not just asking for an answer. I don't understand and any form of help would be appreciated :)

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  1. geerky42
    • one year ago
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    Do you know about center part?

  2. geerky42
    • one year ago
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    Saying we have center \((h,k)\), then equation would be \((x-h)^2+(y-k)^2 = r^2\) Right?

  3. anonymous
    • one year ago
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    I think that I might understand what you're getting at.. are you implying that the answer would be "a. (x-2)^2+(y-(-5))^2=25" or would it be "c. (x-2)^2+(y-(-5))^2=241" ...?

  4. geerky42
    • one year ago
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    Yeah, we are either at A or C, we don't know yet because we haven't figure out the radius part.

  5. geerky42
    • one year ago
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    \(r\) in \((x-h)^2+(y-k)^2 = r^2\) stands for radius. You can find radius by using distance formula on points \((2,-5)\) and \((-2,10)\)

  6. geerky42
    • one year ago
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    Distance formula is \[d = \sqrt{(x_2-x_1)^2+(y_2-y_1)^2}\]

  7. Loser66
    • one year ago
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    You can use directly the general equation of a circle to get r by replace the point into the formula |dw:1432952523897:dw|

  8. geerky42
    • one year ago
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    yeah, that's better way to figure out radius.

  9. anonymous
    • one year ago
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    (2,-5)=x1 and y1 and (-2,10)=x2 and y2 (-2(-2))^2+(10-(-5))^2 0=25 25 so, would the answer be "a. (x-2)^2+(y-(-5))^2=25" ?

  10. geerky42
    • one year ago
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    \((x_2-x_1)\) part is supposed to be -4. \((-2) - 2 = -4\), right? and \(y_2-y_1\) is supposed to be 15, since 10 - (-5) = 10 + 5 = 15

  11. anonymous
    • one year ago
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    -4^2+15^2 ?

  12. geerky42
    • one year ago
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    \((-4)^2+(15)^2\), yeah.

  13. geerky42
    • one year ago
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    Do you understand?

  14. anonymous
    • one year ago
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    I think so... I still get answer choice a as my answer each time I work this out.. is that correct or am I still totally lost?

  15. geerky42
    • one year ago
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    Let's just do @Loser66 's way. Plug \((-2,10)\) into \((x-2)^2+(y+5)^2\).

  16. geerky42
    • one year ago
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    And solve. What do you get?

  17. anonymous
    • one year ago
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    -4^2+15^2 16+225 241 oh wow..... I see where I messed up! Thank you both so much for helping me and remaining patient :)

  18. geerky42
    • one year ago
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    No problem

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