Day 2 (Elimination)
Ax + By = C constant substitutionrepeating
5x + 12y = 72 3x – 2y = 18 Eliminate y. Scale second equation 5x + 12y = 72 6(3x – 2y = 18) 18x – 12y = 108
5x + 12y = 72 18x – 12y = 108
5x + 12y = 72 3x – 2y = 18 ( ) x3= ( ) x-5= 15x + 36y = x + 10y = y = 126 y = 126/46
2x + 5y = 31 4x + 2y = 38 -2(2x + 5y = 31) -4x – 10y = -62 4x + 2y = 38
-4x – 10y = -62 4x + 2y = 38
2x + 5(3) = 31 2x + 15 = 31 2x = 16 x = 8
5 min
NO INFINITE Take 5 min to try 3, 4, and 5 INDEPENDENTLY Take 3 min to check 3, 4, and 5 with a partner
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
-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
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)
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
Killer’s total (t) = Croaker’s total (t) = m m 11 months! -87m + t = m +t = m = 253 ( ) x-1 87m – t = m +t = 282 m = 11
HoMEWORK Problems on the half sheet of paper. Write on a notebook paper. DUE TOMORROW