SOLUTION: If five times the square of a positive number is added to the product of 31 and the number, the result is 28. Find the number. Options are: 4/5 -4 -7/5 7

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Question 1003671: If five times the square of a positive number is added to the product of 31 and the number, the result is 28. Find the number.
Options are:
4/5
-4
-7/5
7
Found 2 solutions by stanbon, MathLover1:
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
If five times the square of a positive number is added to the product of 31 and the number, the result is 28. Find the number.
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Equation:
5x^2 + 31x - 28 = 0
(5x-4)(x+7) = 0
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Ans: x = 4/5
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Cheers,
Stan H.
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Options are:
4/5
-4
-7/5
7

Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!

If 5 times the square of a positive number x is added to the product of 31 and the number x, and the result is 28, we have
5x%5E2%2B31x=28...........solve for x
5x%5E2%2B31x-28=0....factor completely
5x%5E2-4x%2B35x-28=0
%285x%5E2-4x%29%2B%2835x-28%29=0
x%285x-4%29%2B7%28x-4%29=0
%28x%2B7%29%285x-4%29+=+0
solutions:
if %28x%2B7%29+=+0=>x=-7
if%285x-4%29+=+0=>5x=4=>x=4%2F5

Options are:
4%2F5=> your option
-4
-7/5
7