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Set 13: Quadratic Equations (Intermediate)

Explanation

Answer: B

Solve: x2+8x+16=0x^2 + 8x + 16 = 0

A.

x=4x = 4

B.

x=4x = -4

✓ Correct
C.

x=4,4x = 4, -4

D.

x=8,2x = 8, 2

Detailed Explanation

Choice B is correct. Choice B is the correct answer. This quadratic is a Perfect Square Trinomial. 1. Notice that half of 8 is 4, and 42=164^2 = 16. 2. This fits the pattern (a+b)2=a2+2ab+b2(a+b)^2 = a^2 + 2 ab + b^2. 3. Factor as (x+4)2=0(x + 4)^2 = 0. 4. Take the square root: x+4=0x=4x + 4 = 0 \Rightarrow x = -4. Since the factor is squared, -4 is a "repeated root" (multiplicity 2). Choice A is incorrect because of a sign error. Choice C is incorrect because a perfect square equal to zero has only one distinct solution. Choice D is incorrect because these values do not satisfy the equation.

Key Steps:

The correct answer is x=4x = -4

Why others are wrong:
A: Choice A 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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