SOLUTION: For the given rational function f, find all values of x for which f(x) has the indicated value. f(x) = 5x + 21/x; f(x) = -38

Question 244770: For the given rational function f, find all values of x for which f(x) has the indicated value. f(x) = 5x + 21/x; f(x) = -38
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
For the given rational function f, find all values of x for which f(x) has the indicated value. f(x) = 5x + 21/x; f(x) = -38
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Substitute and solve for "x":
-38 = 5x + 21/x
Multiply thru by "x":
-38x = 5x^2 + 21
Rearrange:
5x^2 + 38x + 21 = 0
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Use the quadratic formula:
x = [-38 +- sqrt(38^2 - 4*5*21)]/10
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x = [-38 +- sqrt(-419)]/10
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x = [-38 +- 20.493i]/10
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x = [-3.8 +- 2.049i]
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Cheers,
Stan H.
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