Answer:
A=-2
B=-8
Step-by-step explanation:
In order for the system of linear equations to have infinitely many solution, they must be the same equation.
Ax-y=8
2x+y=B
We need to choose A and B so they are the same equation.
I notice they are both in the same form but in the second column you have opposites;
the -y and y.
So im going to multiply either equation by -1 so that part is exactly the same.
Don't choose both; choose only one.
Let's multiply the first equation by -1.
Doing this gives us the following:
-Ax+y=-8
2x+y=B
So now we can choose A and B so these equations appear exactly the same.
We need -A=2 and B=-8.
-A=2 implies A=(opposite of 2) which is -2.
Conclusion:
A=-2
B=-8
Answer:
1) {y,x}={-3,-23}
2) {x,y}={7,-9/2}
Step-by-step explanation:
Required:
- Solve systems of equations
1) y - x = 20, 2x - 15y = -1
Equations Simplified or Rearranged :
[1] y - x = 20
[2] -15y + 2x = -1
Graphic Representation of the Equations :
x + y = 20 2x - 15y = -1
Solve by Substitution :
// Solve equation [1] for the variable y
[1] y = x + 20
// Plug this in for variable y in equation [2]
[2] -15•(x +20) + 2x = -1
[2] - 13x = 299
// Solve equation [2] for the variable x
[2] 13x = - 299
[2] x = - 23
// By now we know this much :
y = x+20
x = -23
// Use the x value to solve for y
y = (-23)+20 = -3
Solution :
{y,x} = {-3,-23}
2) 25-x=-4y,3x-2y=30
Equations Simplified or Rearranged :
[1] -x + 4y = -25
[2] 3x - 2y = 30
Graphic Representation of the Equations :
4y - x = -25 -2y + 3x = 30
Solve by Substitution :
// Solve equation [1] for the variable x
[1] x = 4y + 25
// Plug this in for variable x in equation [2]
[2] 3•(4y+25) - 2y = 30
[2] 10y = -45
// Solve equation [2] for the variable y
[2] 10y = - 45
[2] y = - 9/2
// By now we know this much :
x = 4y+25
y = -9/2
// Use the y value to solve for x
x = 4(-9/2)+25 = 7
Solution :
{x,y} = {7,-9/2}
So with this, you can rewrite the equation as: 
Firstly, solve the multiplication: 
Next, combine like terms, and <u>your answer will be: 
</u>
The best way to answer this would be making a graph
For 1 sign it costs 54.50 and he makes 15
For 2 signs it costs 59 and he makes 30
For 3 signs it costs 63.50 and he makes 45
For 4 signs it costs 68 and he makes 60
For 5 signs it costs 72.50 and he makes 75
This means that after 5 signs Larry will be making profit
{(-5,64), (2,1)}
linear equation: y = -9x + 19
quadratic equation: y = x² - 6x + 9
Substitute the y in the quadratic equation by the its value in the linear equation.
-9x + 19 = x² - 6x + 9
- 19 - 19 *subtract 19 to both sides
-9x = x² - 6x -10
+9x + 9x *add 9x to both sides
0 = x² + 3x - 10
0 = (x + 5) (x - 2) *Factor
Set each factor = 0 and solve
x + 5 = 0 ; x - 2 = 0
x = -5 ; x = 2
Find the corresponding value of y using the linear equation.
y = -9x + 19
x = -5 x = 2
y = -9(-5) + 19 y = -9(2) + 19
y = 45 + 19 y = -18 + 19
y = 64 y = 1
(-5,64) (2,1)
Check each value on each equation.
y = x² - 6x + 9
(-5,64) (2,1)
64 = (-5)² - 6(-5) + 9 1 = 2² - 6(2) + 9
64 = 25 + 30 + 9 1 = 4 - 12 + 9
64 = 64 1 = 1
y = -9x + 19
64 = -9(-5) + 19 1 = -9(2) + 19
64 = 45 + 19 1 = -18 + 19
64 = 64 1 = 1
{(-5,64), (2,1)}
