Posted by Algebra PLEASE HELP!! on Sunday, March 18, 2012 at 11:29pm.
2 x – 3 y = 10 Multiply both sides by 2
4 x - 6 y = 20
5 x + 2 y = 6 Multiply both sides by 3
15 x + 6 y = 18
4 x - 6 y = 20
+
15 x + 6 y = 18
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4 x + 15 x - 6 y + 6 y = 20 + 18
19 x = 38 Divide both sides by 19
x = 38 / 19
x = 2
To get the value of y you need to use the substitution method.
Substitute x = 2
into equation
2 x - 3 y = 10
2 * 2 - 3 y = 10
4 - 3 y = 10
- 3 y = 10 - 4
- 3 y = 6 Divide both sides by - 3
y = 6 / - 3
y = - 2
The point of intersection of the graphs of the equations of the system
Ax – 4y = 9
4x + By = –1
is (–1, –3). Explain how to find the values of A and B, then find these values.
(-1 , -3) = ( x,y)
put the X and Y values into the first equation,
Ax-4y=9
A(-1)- 4(-3)= 9
-A + 12=9
-A=-3
A= 3 [ Multiply by (-1)]
Now put the X and Y values to the second equation,
4( -1) +B( -3) =-1
-4- 3B=-1
-3B= 3
B=-1 [ Multiply by negative (-1)]
Just check are those ans is right, put the all values to the equation......
3(-1)-4(-3)=9
9=9
And, 4(-1)+(-1)(-3)=-1
-4 + 3=-1
-1 = -1
So, (A,B)= ( 3, -1 )