1. Prerequisite Skills VOCABULARY CHECK Copy and complete the statement. 2. Two lines in the same plane are if they do not intersect. ? ? The least common multiple of 10 and 15 is. 1. 30 ANSWER parallel ANSWER

2. 3. x – y = 4 Prerequisite Skills SKILL CHECK Graph the equation. 4. 6x – y = –1

3. Prerequisite Skills SKILL CHECK Graph the equation. 6. 3x – 2y = –12 5. 4x + 5y = 20

4. 7. 5m + 4 – m = 20 Prerequisite Skills SKILL CHECK Solve the equation. 8. 10(z +5) + z = 6 4 ANSWER –4–4

5. 9. y = 2x –3, y + 2x = –3 Prerequisite Skills SKILL CHECK Tell whether the graphs of the two equations are parallel lines. Explain your reasoning. 10. y – 5x = –1, y – 5x = 1 Not parallel; the slope of the graph of the first equation is 2, while the slope of the graph of the second equation is  2. ANSWER Parallel; the 2 lines have a slope of 5, but different y -intercepts. ANSWER

6. Prerequisite Skills SKILL CHECK Tell whether the graphs of the two equations are parallel lines. Explain your reasoning. 11. y = x + 10, x – y = –9 12. 6x – y = 4, 4x – y = 6 Parallel; the 2 lines have a slope of 1, but different y -intercepts. ANSWER Not parallel; the slope of the graph of the first equation is 6, while the slope of the graph of the second equation is 4. ANSWER

7. Prerequisite Skills SKILL CHECK Graph the inequality. 14. x – y < 5 13. y  –2x + 1

8. Prerequisite Skills SKILL CHECK Graph the inequality. 16. y > 3 15. x  –4