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Solving Radical Equations Square root x+7 = x - 5
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Solving Radical Equations Square root x+7 = x - 5
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Jul 20, 2015
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Solving Radical Equations
Square root x+7 = x - 5
Mathematics
high-school
Stoatman
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Stoatman
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The domain:
The radicand must be greater than or equal to 0.
The value of the square root must be greater than or equal to 0.
Therefore x≥5.
2<5 so it's not a correct solution.
9≥5 so it's a correct solution.
The answer:
x=9
Pcgben
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Jul 22, 2015
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Pcgben
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so the square root of the quatity(x+7)=x-5
so you square both sides and get rid of the square root
x+7=(x-5)^2
(x-5)^2=x^2-10x+25
x+7=x^2-10x+25
subtract 7 from both sides
x=x^2-10x+18
subtract x from both sides
0=x^2-11x+18
so if xy=0 we can assume that x or/and y =0
factor out x^2-11+18
(find what two numbers multiply to get 18 and add to get -11)
-2 times -9=18
-2+(-9)=-11
(x-2)(x-9)=0
set them to zero
x-2=0
x=2
x-9=0
x=9
there are two answers -2 and -9
Tbk
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Jul 27, 2015
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Tbk
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