Math 060 Quiz 5 Answer Key

MATH 060

ANSWER KEY

TTh 1:30-3:35, Room A-107

QUIZ 5 (Total 12 points = 10 points + 2 points extra credit) September 30, 2008 1. (3 points) Solve this system of equations by drawing graphs: x+y=1 y = 2x – 5

The lines intersect at (2, –1). The solution is: x=2 y = –1

2. Answer one part at a time; don’t just jump in and solve the equations. Suppose you are given this system and are asked to solve by substitution. y – 3x = 11 x – 2y = –7 a. (1 point) Use the first equation to get y = __3x + 11__________ b. (2 points) Substitute what you got in part (a) into the second equation. x – 2(3x + 11)= –7

c. (1 point) Use the second equation to get x = __2y – 7__________ d. (2 points) Substitute what you got in part (c) into the first equation. y – 3(2y – 7) = 11

e. (3 points) Use what you got in part (d) to solve for y and then x. y – 6y + 21 = 11 –5y = –10 y=2 x = 2y – 7 = 4 – 7 = –3

.