7

Set 3: Systems of Equations

Explanation

Answer: B

Identify the relationship between the lines: {y=3x+4y=3x2\begin{cases} y = -3x + 4 \\ y = -3x - 2 \end{cases}

A.

The lines are perpendicular

B.

The lines are parallel

✓ Correct
C.

The lines are identical

D.

The lines intersect at one point

Detailed Explanation

Choice B is correct. Choice B is the correct answer. Both equations are in slope-intercept form y=mx+by = mx + b. Analysis: - First line: slope m1=3m_1 = -3, y-intercept b1=4b_1 = 4 - Second line: slope m2=3m_2 = -3, y-intercept b2=2b_2 = -2 Comparison: - m1=m2=3m_1 = m_2 = -3 → same slope - b1b2b_1 \neq b_2 → different y-intercepts When lines have the same slope but different y-intercepts, they are parallel. Strategic Tip: - Parallel lines: same slope, different intercepts - Perpendicular lines: slopes are negative reciprocals (m1m2=1m_1 \cdot m_2 = -1) - Identical lines: same slope AND same intercept Choice A is incorrect because perpendicular lines have slopes that multiply to 1-1. Here, (3)×(3)=91(-3) \times (-3) = 9 \neq -1. Choice C is incorrect because identical lines must have the same y-intercept. Choice D is incorrect because parallel lines never intersect.

Key Steps:

The correct answer is The lines are parallel

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

🎯 Keep Practicing!

Master all sections for your best SAT score