ExplainItLikeImFive
Solve the equation. Identify any extraneous solutions.
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ExplainItLikeImFive
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A. 6 is a solution to the original equation. The value –5 is an extraneous solution.
B. 6 and 5 are both extraneous solutions.
C. 5 is a solution to the original equation. The value –6 is an extraneous solution.
D. 6 and –5 are solutions.
dan815
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do u know the meaning of extraneous
ExplainItLikeImFive
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That it's unrelated, I think.
cwrw238
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square both sides
x^2 = x+ 30
x^2 -x - 30 = 0
can u solve this?
cwrw238
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extraneous means that although the working out gives it as a solution , it is not possible as a root
cwrw238
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not quite
(x - 6)(x + 5) = 0
giving x = 6 , -5
ExplainItLikeImFive
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So what do I do with that?
cwrw238
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well see if these roots are possible by substituting each into the original equation
cwrw238
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eg x = 6
6 = sqrt(6 + 30)
6 = 6 - so that is a genuine root
ExplainItLikeImFive
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So I can eliminate B and C
cwrw238
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yes
cwrw238
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is -5 a solution?
cwrw238
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try plugging in -5 for x in the original equation
cwrw238
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- 5 = sqrt (-5 + 30) does that work out?
cwrw238
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what are the square roots of 25?
cwrw238
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5 ANd -5 right?
cwrw238
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so its a genuine root
ExplainItLikeImFive
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So they're both genuine making them both solutions.
cwrw238
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right
ExplainItLikeImFive
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I do believe I'd pick D
cwrw238
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correct
ExplainItLikeImFive
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Thank you very much.
cwrw238
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yw
Laaislima
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wrong.
cwrw238
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please explain why thats wrong
Laaislima
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ask the teacher, I answered D and I got it wrong.
dan815
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hii
dan815
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|dw:1377219675010:dw|
dan815
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is this your question?
dan815
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oh sorry this is your question |dw:1377219778699:dw|
dan815
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your answers are 6 and -5!
dan815
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|dw:1377219879123:dw|
Laaislima
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The right answer should be 6 is a solution to the original equation. The value –5 is an extraneous solution.