5

Set 6: Systems of Equations

Explanation

Answer: C

What is the intersection point of the lines y=3x+15y = -3x + 15 and y=2xy = 2x?

A.

(4,8)(4, 8)

B.

(2,4)(2, 4)

C.

(3,6)(3, 6)

✓ Correct
D.

(5,10)(5, 10)

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: 3x+15=2x-3 x + 15 = 2 x Step 2: Solve for xx: $$$15= 2 x + 3 x15= 5 x$x = 3 Step 3: Find yy using either equation (using the second): y=2(3)=6y = 2(3) = 6 Solution: (3,6)(3, 6) Verification: 6=3(3)+15=9+15=66= -3(3) + 15 = -9 + 15 = 6 ✓ Strategic Tip: The intersection is where both lines share the same point. Choice A is incorrect because 8=2(4)=88= 2(4) = 8 ✓, but 83(4)+15=38\neq -3(4) + 15 = 3. Choice B is incorrect because 4=2(2)=44= 2(2) = 4 ✓, but 43(2)+15=94\neq -3(2) + 15 = 9. Choice D is incorrect because 10=2(5)=1010= 2(5) = 10 ✓, but 103(5)+15=010\neq -3(5) + 15 = 0.

Key Steps:

The correct answer is (3,6)(3, 6)

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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