Question 896858: need to explain how to use matrix equation to show that lines represented by y=-3x+4 and y=-4x-8 intersect
Answer by richwmiller(17219)   (Show Source):
You can put this solution on YOUR website! y=-3x+4 and y=-4x-8
first put them in order
x+y=b
3x+y=4
4x+y=-8
3,1,4
4,1,-8
A solution to these equations is the intersection of the lines
3,1,4
4,1,-8
divide row 1 by 3
1,1/3,4/3
4,1,-8
add down (-4) *row 1 to row 2
1,1/3,4/3
0,-1/3,-40/3
divide row 2 by -1/3
1,1/3,4/3
0,1,40
We now have the value for the last variable.
We will work our way up and get the other solutions.
add up (-1/3) *row 2 to row 1
1,0,-12
0,1,40
final
1,0,-12
0,1,40
1,0,-12
0,1,40
"-12","40"
(-12,40)
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