An item has a listed price of $30. If the sales tax rate is 5%, how much is the sales tax (in dollars)?
2 answers:
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9514 1404 393
Answer:
x = -1
Step-by-step explanation:
A graphical solution can avoid extraneous solutions. The attachment shows the one solution is x = -1.
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Squaring both sides gives ...
x +5 = (x +3)² = x² +6x +9
Putting this in standard form, we have ...
x² +5x +4 = 0
(x +1)(x +4) = 0 . . . . . factor
x = -1 or -4 . . . . . . . . values of x that make the factors zero
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Since we require the root to be non-negative, we must have ...
x +3 ≥ 0
x ≥ -3
The only solution that satisfies this requirement is x = -1. The solution x = -4 is extraneous. The solution is x = -1.
