SOLUTION: When the sum of 397 and four times a positive number is subtracted from the square of the number, the result is 128. Find the number

Question 942649: When the sum of 397 and four times a positive number is subtracted from the square of the number, the result is 128. Find the number
Found 2 solutions by TimothyLamb, stanbon:
Answer by TimothyLamb(4379) (Show Source): You can put this solution on YOUR website!
xx - (4x + 397) = 128
xx - 4x - 397 - 128 = 0
xx - 4x - 525 = 0
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the above quadratic equation is in standard form, with a=1, b=-4 and c=-525
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to solve the quadratic equation, by using the quadratic formula, copy and paste this:
1 -4 -525
into this solver: https://sooeet.com/math/quadratic-equation-solver.php
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the quadratic has two real roots at:
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x = 25
x = -21
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the negative root doesn't fit the problem statement, so use the positive root:
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answer:
x = 25
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Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
When the sum of 397 and four times a positive number is subtracted from the square of the number, the result is 128. Find the number
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Equation:
x^2 - (397+4x) = 128
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x^2 - 4x - 397 = 128
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x^2 - 4x - 525 = 0
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(x - 25)(x+21) = 0
Positive solution::
x = 25
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Cheers,
Stan H.
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