Math Systems of Equations Khan Academy Ms. Docampo

Home Instruction Solution

Quiz 2 Teacher: 5x + 2y = 4 and 4x + y = 2

Multiply 2^nd equation by 2

8x +2y = 4

5x + 2y=4

3x = 0 (subtracted 2^nd equation from the first) divide both sides by 3 get x=0

substitute x=0 into equation 1 get 5(0)+2y=4 means 2y = 4 means y = 2 (0,2)SolutionT

Lucius

4x + y = -1, 10x + 4y = 8 multiply the 1^st equation by 4

16x + 4y = -4

10x + 4y = 8 subtracted the 2^nd equation to get

6x = -12 dividing by 6, get x = -2 Therefore Lucius CANNOT match teacher.

Angelina

12x + 3y = 6 and 5x + 2y = 4 multipy 1^st eqution by 2, 2^nd by 3 getting

24x+ 6y = 12

15x+ 6y = 12 now subtracted

9x = 0 divide by 9 get x = 0 (so far so good)

substitute x = 0 to find y solution

15(0) + 6y = 12 means 6y =12 divide by 6 means y = 2 means (0,2) SolutionA MATCHED TEACHER

Which System has the same solution as the teacher's system?

A) Only Lucius

B) Only Angelina

100. Both Lucius and Angelina's
     D) Neither Lucius nor Angelina's

ANSWER: B