what is the equation of the vertical line passing through the point (1, -1).

Question

jim766 · Answer

a vertical line is going to start with 

x= 

it passes through the point (1, -1) , the x  being 1

so the equation would be

x = 1

jim766 · Answer

question?

anonymous · Answer

ah i love you thanks ! can you help with two more?

jim766 · Answer

I can try

anonymous · Answer

Choose the equation below that represents the line passing through the point (-3, -1) with a slope of 4.

jim766 · Answer

you can do this a couple different ways...do you want to use 
point slope form or
y = mx + b?

anonymous · Answer

which is easier?

jim766 · Answer

I like y = mx + b, but they are about the same amount of work. 

To write an equation of a line you need a slope and a y intercept.
They gave you a slope in the problem, so all you need is the y intercept

y = mx + b
      m is slope
      b is y intercept

any of this familair?

anonymous · Answer

not really, im taking the pretest right now i havent been taught the lesson yet

jim766 · Answer

in the point you gave do you know which is x and which is y?

anonymous · Answer

-3 x and -1 y

jim766 · Answer

right, so just substitute them into  

y = mx + b
-1 = 4(-3) + b     

can you solve this for b?

jim766 · Answer

-1 = -12 +b
+12   +12
11 = b

right?

jim766 · Answer

the m is 4, the b is 11  all you do now is subtitute those into
y = mx + b
y = 4x + 11

anonymous · Answer

ohh

anonymous · Answer

now look y - 1 = 4(x - 3) 
y + 1 = 4(x + 3) 
y - 3 = 4(x + 1) 
y + 3 = 4(x - 1)

anonymous · Answer

those are my options so i dont have to solve it..

jim766 · Answer

ok those are point slope form

y - y1 = m(x - x1)
y -(-1) = 4(x - 3)
y + 1 = 4(x -3)

its the first option

anonymous · Answer

thank you sooo much !

anonymous · Answer

but its y-1 not +1  right ?

jim766 · Answer

the formula has a minus sign and the y is -1
      y - - 1 = 4(x -3)
      
minus a negative changes to addition

      y + 1 = 4(x -3)

jim766 · Answer

make sense?

anonymous · Answer

i guess but its not one of the options

anonymous · Answer

its either 
y - 1 = 4(x - 3)  or y + 1 = 4(x + 3)

jim766 · Answer

sorry I lost the negative sign on the 3 on your point above

it should be y + 1=4(x + 3)

sorry for the confusion

anonymous · Answer

its ok thanks so much