1. Day 2 (Elimination)

2. Ax + By = C constant substitutionrepeating

3. 5x + 12y = 72 3x – 2y = 18 Eliminate y. Scale second equation 5x + 12y = 72 6(3x – 2y = 18)  18x – 12y = 108

4. 5x + 12y = 72 18x – 12y = 108

5. 5x + 12y = 72 3x – 2y = 18 ( ) x3= ( ) x-5= 15x + 36y = 216 -15x + 10y = -90 46y = 126 y = 126/46

6. 2x + 5y = 31 4x + 2y = 38 -2(2x + 5y = 31)  -4x – 10y = -62 4x + 2y = 38

7. -4x – 10y = -62 4x + 2y = 38

8. 2x + 5(3) = 31 2x + 15 = 31 2x = 16 x = 8

9. 5 min

10. NO INFINITE Take 5 min to try 3, 4, and 5 INDEPENDENTLY Take 3 min to check 3, 4, and 5 with a partner

11. 2x – 4y =6 -3x +6y = -9 (2x – 4y =6)/2  (-3x +6y = -9)/3  x – 2y =3 -x +2y = -3 0 = 0 Always true  infinite solutions

12. -9x + 15y = 13 3x – 5y = -6 -9x + 15y =13 (3x – 5y = -6) x3  0 = -5 Never true  no solutions -9x + 15y =13 9x – 15y = -18

13. 5x + 2y = 12 -5x + 4y = 12 6y = 24 5x + 2y =12 -5x + 4y = 12 y =4 5x + 2(4) = 12 5x + 8 = 12 5x = 4 x = 4/5 (4/5, 4)

14. knights= k and squires= s 3k + 2s = 32 2k + 1s = 19( ) x-2  -4k – 2s = -38 3k + 2s = 32 -k = -6 k = 6 3(6) + 2s = 32 2s = 14 s = 7

15. Killer’s total (t) = Croaker’s total (t) = 29 + 87m 282 + 64m 11 months! -87m + t = 29 -64m +t = 282 23m = 253 ( ) x-1  87m – t = -29 -64m +t = 282 m = 11

16. HoMEWORK Problems on the half sheet of paper. Write on a notebook paper. DUE TOMORROW