7

Set 9: Linear Inequalities

Explanation

Answer: A

Solve: x2=2x7|x - 2| = 2x - 7

A.

x=5x = 5

✓ Correct
B.

x=3x = 3

C.

x=5x = 5 or x=3x = 3

D.

No solution

Detailed Explanation

Choice A is correct. Choice A is the correct answer. Check for extraneous solutions. 1. Case 1: x2=2x7x=5x=5x - 2 = 2 x - 7 \rightarrow -x = -5 \rightarrow x = 5 - Check: 52=2(5)73=3|5-2| = 2(5)-7 \rightarrow 3 = 3 (Valid) 2. Case 2: x2=(2x7)x2=2x+73x=9x=3x - 2 = -(2 x - 7) \rightarrow x - 2 = -2 x + 7 \rightarrow 3 x = 9 \rightarrow x = 3 - Check: 32=2(3)71=1|3-2| = 2(3)-7 \rightarrow 1 = -1 (Invalid!) 3. Result: Only x=5x = 5 Strategic Tip: Always plug answers back into absolute value equations. A=B|A| = B requires B0B \geq 0. Choice B is incorrect because it is an extraneous solution. Choice C is incorrect because it includes the extraneous solution. Choice D is incorrect because x=5x=5 is valid.

Key Steps:

The correct answer is x=5x = 5

Why others are wrong:
B: Choice B is incorrect and may result from a calculation error.
C: Choice C is incorrect and may result from a calculation error.
D: Choice D is incorrect and may result from a calculation error.

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