Finding the equation of a line.?

Question

1) the equation of a line which contains the point (2,4) and (-2,2)

2) What type of lines have a slope of zero?

3) Do The equation y = ¾x - 3 crosses the y axis at 3

4)Write the equation of a line with the slope of -2 which contains the point (3,6)

Show all work to receive credit for this problem.

Answer 1

Hello

1) Our general equation is y=mx+b.
First lets find the slope (2-4) / (-2-2) = -2/-4 = 1/2

Now plug in either (2,4) or (-2,2) to get
4 = (1/2)*2 + b ----- thus b = 3

So the equation is y = (1/2) x +b.

2) Horizontal lines (y = any number)

3) No - the y intercept is at -3. So it crosses at 0,-3.

4) So we have 6 = -2*3 + b -- thus b = 12
So the equation is y = -2x +12

Hope this helps

Answer 2

1) the equation of a line which contains the point (2,4) and (-2,2)

(y - 4) / (x - 2) = 2 / 4

2) What type of lines have a slope of zero?

horizontal lines, or lines parallel to the x-axis

3) Do The equation y = ¾x - 3 crosses the y axis at 3

No. The y-intercept for this equation is - 3.

4)Write the equation of a line with the slope of -2 which contains the point (3,6)

(y - 6) / (x - 3) = - 2

Answer 3

1) get the slope;
m= (2-4)/(-2-2)
m= 1/2
make an equation using point slope form;
(y-4)= (1/2)(x-2)
y-4=(x-2)/2
2y-8=x-2
x-2y+6=0
2) horizontal
3)no, because the formula of y intercept form is;
y=mx+b where: b is y intercept
and your equation is;
y=(5/4)x-3 where:b= -3
therefore it crosses the y-axis at -3.
4)using point slope form;
(y-6)= -2(x-3)
y-6= -2x+6
2x+y=12

Answer 4

1) EDIT: i used the wrong slope formula :O thx for clearing that up, jeff. LOL
OMG EDIT AGAIN: no i didnt use the wrong slope formula...but im not going to do the problem again =P

2) Umm lines like y = 3. I don't really know how to answer that question. =P

3) No, it crosses at (0, -3)

4) y = -2x + 12


Uhhh I think that stuff is right. I haven't done math in a little while. :)