The coordinates below represent two linear equations. how many solutions does this system of equations have?
line 1
x y
–4 8
4 6
line 2
x y
–1 1
3 5
a.
0
b.
exactly 1
c.
exactly 2
d.
infinitely many
question

find the equations of the lines in slope-intercept form which is y=mx+b where m=slope b=y intercept
the choices:
0 solutions: means the lines don't intercect at all, meaning same slope but different y intercept or they ar paralell
1 solution: lines intercect in 1 point
2 solutions: curvy line with a straight line thorugh middle
infinetly solutions: same line
 

to find slope you do
slope=(y1-y2)/(x1-x2)
first line is
(-4,8)
(4,6)
(x,y)
x1=-4
y1=8
x2=4
y2=6
subsitute
(8-6)/(-4-4)=2/-8=-1/4
slope=-1/4
subsitute
y=-1/4x+b
subsitute one of the points
(4,6)
x=4
y=6
6=-1/4(4)+b
6=-1+b
add 1 to both sides
7=b
y=-1/4+7

now solve for the other equation

(-1,1)
(3,5)
x1=-1
y1=1
x2=3
y2=5
subsitute
(1-5)/(-1-3)=(-4)/(-4)=4/4=1
y=1x+b
subsitute
(-1,1)
x=-1
y=1
1=1(-1)+b
1=-1+b
add 1
2=b
y=x+2

we have the lines
y=-1/4x+7 and
y=x+2
solve for a common solution
y=x+2 and y=-1/4x+7 therefor
x+2=-1/4x+7
subtract 7 from both sides
x-5=-1/4x
mulitply both sides by -4
-4x+20=x
add 4x to both sides
20=5x
divide both sides by 5
4=x
subsitute
y=x+2
y=4+2
y=6
the soluiton is (4,6)
there is only one solution
the answer is B

B) greg: 30 points , tremaine 38 points