4

Set 10: Systems of Equations (Intermediate)

Explanation

Answer: C

For what value of kk does the system have infinitely many solutions? {4x+2y=82x+y=k\begin{cases} 4x + 2y = 8 \\ 2x + y = k \end{cases}

A.

k=2k = 2

B.

k=8k = 8

C.

k=4k = 4

✓ Correct
D.

k=6k = 6

Detailed Explanation

Choice C is correct. Choice C is the correct answer. For infinitely many solutions, the second equation must be a multiple of the first (or vice versa). Step 1: Notice that the first equation's coefficients are double the second: - First: 4x+2y=84x + 2 y = 8 - Second: 2x+y=k2x + y = k Step 2: Divide the first equation by 2: \frac{4 x + 2 y}{2} = \frac{8}{2}$2x + y = 4$$$ Step 3: For the equations to be identical: k = 4$$ With k=4k = 4, both equations represent the same line, giving infinitely many solutions. Strategic Tip: For infinitely many solutions, one equation must be a scalar multiple of the other (including the constant term). Choice A is incorrect because k=2k = 2 would make the lines parallel (no solution), not identical. Choice B is incorrect because k=8k = 8 would make the lines parallel (no solution). Choice D is incorrect because k=6k = 6 would make the lines parallel (no solution).

Key Steps:

The correct answer is k=4k = 4

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