6

Set 12: Systems of Equations (Intermediate)

Explanation

Answer: D

For what value of kk does the system have no solution? {3x2y=76x4y=k\begin{cases} 3x - 2y = 7 \\ 6x - 4y = k \end{cases}

A.

k=7k = 7

B.

k=10k = 10

C.

k=14k = 14

D.

Any value except 14

✓ Correct

Detailed Explanation

Choice D is correct. Choice D is the correct answer. For no solution, the system must represent parallel lines (same coefficients on xx and yy, but different constants). Step 1: Notice that the second equation has coefficients that are exactly double the first: - First equation: 3x2y=73x - 2 y = 7 - Second equation: 6x4y=k6x - 4 y = k Step 2: If we multiply the first equation by 2: $$2(3 x - 2 y) = 2(7)6x - 4 y = 14$$$ Step 3: For the lines to be parallel but not identical: - If k = 14:thelinesareidenticalinfinitelymanysolutionsIf: the lines are identical → infinitely many solutions - If k \neq 14:thelinesareparallelnosolutionStrategicTip:Parallellinesoccurwhenleftsidesareproportionalbutrightsidesarenot.ChoiceAisincorrectbecause: the lines are parallel → no solution Strategic Tip: Parallel lines occur when left sides are proportional but right sides are not. Choice A is incorrect because k = 7givesnosolution(not14),butitsnottheonlyvalue.ChoiceBisincorrectbecausegives no solution (not 14), but it's not the only value. Choice B is incorrect becausek = 10givesnosolution,butitsnottheonlyvalue.ChoiceCisincorrectbecausegives no solution, but it's not the only value. Choice C is incorrect becausek = 14$ gives infinitely many solutions, not no solution.

Key Steps:

The correct answer is Any value except 14

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.
C: Choice C is incorrect and may result from a calculation error.

🎯 Keep Practicing!

Master all sections for your best SAT score