10

Set 11: Systems of Equations (Intermediate)

Explanation

Answer: C

Solve by elimination: {2x+5y=212x5y=9\begin{cases} 2x + 5y = 21 \\ 2x - 5y = 9 \end{cases}

A.

(2,10)(2, 10)

B.

(4,18)(4, 18)

C.

(3,14)(3, 14)

✓ Correct
D.

(1,12)(1, 12)

Detailed Explanation

Choice C is correct. Choice C is the correct answer. To find the intersection, we set the two expressions for yy equal to each other. Step 1: Set the equations equal: 4x+2=x+114x + 2 = x + 11 Step 2: Solve for xx: $$$4x - x = 11 - 23x = 9$x = 3 Step 3: Find yy using either equation (using the second): y=3+11=14y = 3 + 11 = 14 Solution: (3,14)(3, 14) Verification: 14=4(3)+2=12+2=1414= 4(3) + 2 = 12 + 2 = 14 ✓ Strategic Tip: The intersection point is where both lines have the same coordinates. Choice A is incorrect because 10=4(2)+2=1010= 4(2) + 2 = 10 ✓, but 102+11=1310\neq 2 + 11 = 13. Choice B is incorrect because 18=4+11=151818= 4 + 11 = 15 \neq 18. Choice D is incorrect because 12=1+11=1212= 1 + 11 = 12 ✓, but 124(1)+2=612\neq 4(1) + 2 = 6.

Key Steps:

The correct answer is (3,14)(3, 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.
D: Choice D is incorrect and may result from a calculation error.

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