Substitution
y = 3x + 1
y = 6x + 10
x = -3 , y = -8
4x + 9y = 29
6x - 9y = 21
x = 5, y = 1
x + 5y = 13
x + y = -3
x = -7, y = 4
The sum of two numbers is 45. The difference between the two numbers is 35. What are the numbers?
x +y += 45
x- y= 35
What are three methods for solving simultaneous equations?
Graphing, elimination and substitution method
y = -2x + 13
y = 4x - 11
x = 4, y = 5
2x - 2y = -18
5x + 2y = -24
x = -6, y = 3
x + 4y = 26
x = 6, y = 5
A motorist buys 24 liters of gas and 5 liters of oil for $1070 from AID, while another motorist buys 18 liters of gas and 10 liters of oil for $1240, also from AID. Find the cost of 1 liter of gas and 1 liter of oil at AID.
24x +5y =1070
18x + 10y=1240
When using the elimination method, and after making your coefficients the same. If the signs are the same, will you add or subtract?
Subtract
4x + 2y = -20
y = x - 4
x = -2, y = -6
-8x - 5y = 18
8x + 7y = -22
x = -1, y = -2
-5x - 6y = 14
3x - 6y = -18
x = -4, y = 1
FREE POINTS!
When using the elimination method, and after making your coefficients the same. If the signs are different, will you add or subtract?
ADD
5x - y = 21
y = -7x + 15
x = 3, y = -6
5x - 4y = -8
-5x + 6y = 12
x = 0, y = 2
-8x + 2y = 28
-8x - 7y = 10
x = -3, y = 2
A pigeon can lay either white or brown eggs. Three white eggs and two brown eggs weigh 13 ounces, while five white eggs and four brown eggs weigh 24 ounces. Find the weight of a brown egg and of a white egg.
3a + 2b = 13
5a +4b =24
What's the first step for solving simultaneous equations using the substitution method?
Make one of the variable in one of the equations the subject.
y = -8x - 3
8x + 4y = 12
x = -1, y = 5
4x - 5y = 7
-8x + 5y = 1
x = -2, y = -3
-2x - 4y = 8
-5x - 4y = -10
x = 6, y = -5
Twice a number added to three times another gives 21. Find the numbers, if the difference between them is 3.
2x+3y=21
x-y=3
Quickly explain how you would solve a pair of simultaneous equations given in a word problem.
Answers may vary