4
algebra

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)

D

(5,10)(5, 10)

Correct Answer: C

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-3x + 15 = 2x

Step 2: Solve for xx: 15=2x+3x15 = 2x + 3x15=5x15 = 5xx=3x = 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 because8=2(4)=88 = 2(4) = 8 ✓, but 8 eq3(4)+15=38 \ eq -3(4) + 15 = 3.

Choice B is incorrect because4=2(2)=44 = 2(2) = 4 ✓, but 4 eq3(2)+15=94 \ eq -3(2) + 15 = 9.

Choice D is incorrect because10=2(5)=1010 = 2(5) = 10 ✓, but 10 eq3(5)+15=010 \ eq -3(5) + 15 = 0.