Question 511720
x = a number
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Three times the square of the number minus four times the number = 15.
3*x^2 - 4x = 15
3x^2 -4x -15 = 0
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factor
(3x +5)(x -3) = 3x^2 -9x +5x -15 = 3x^2 -4x -15
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x = -5/3 or 3
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Obviously, -5/3 is not a whole number, so x =3 is the proposed solution.
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Check to see if it is correct.
.3x^2 = 3(9) = 27
4x = 12
27-12 = 15
Correct
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Answer:  The whole number is 3.
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Done.