Do Now
Solve using elimination:
3x + 2y = – 19
– 3x – 5y = 25
Homework Solutions
1)
x – y = 1
+ x + y = 3
2x
= 4
x = 2
2+ y = 3
y = 1
Solution: (2, 1)
Homework Solutions
3)
x + 4y
– x – 6y
10y
y
= 11
= 11
= 0
= 0
x + 4(0) = 11
x = 11
Solution: (11, 0)
Homework Solutions
5)
3x + 4y = 19
– 3x + 6y = 33
-2y = -14
y = 7
3x + 4(7) = 19
3x + 28 = 19
3x = -9
x = -3
Solution: (-3, 7)
Homework Solutions
7)
3a + 4b = 2
+ 4a – 4b = 12
7a
= 14
a = 2
3(2) + 4b = 2
6 + 4b = 2
4b = -4
b = -1
Solution: (2, -1)
Homework Solutions
9)
2x – 3y = 9
– -5x – 3y = 30
7x
= -21
x = -3
2(-3) – 3y = 9
-6 – 3y = 9
-3y = 15
y = -5
Solution: (-3, -5)
6s + 2t = 24
4s + 2t = 18
The coefficients of one of the variables are
not always going to be the same.
When neither variable’s coefficients are the
same, you can’t eliminate one variable just
by adding or subtracting.
Sometimes we have to MULTIPLY one or
both equations to make the coefficients of
one of the variables the same.
3x + 4y = 6
5x + 2y = – 4
3x + 2y = 0
x – 5y = 17
4c – 3d = 22
2c – d = 10
8 x  3 y  11
2 x  5 y  27
4x  5 y  6
6 x  7 y  20
5 x  3 y  12
4 x  5 y  17
3x + 2y = – 9
5x – 3y = 4
Homework
Worksheet pg. 423 #’s 1, 4, 7, 10