Question

What is am equation for the line that passes through points (-1,-4) and (1,4)? Write the equation in slope intercept form.
a. y=4x
b. y=-4x
c. y= -1x -4
d. y= -4x + 1

Answer 1

Can you help?

Answer 2

\(\bf \begin{array}{lllll}
&x_1&y_1&x_2&y_2\\
&({\color{red}{ -1}}\quad ,&{\color{blue}{ -4}})\quad &({\color{red}{ 1}}\quad ,&{\color{blue}{ 4}})
\end{array}
\\\quad \\

slope = {\color{green}{ m}}= \cfrac{rise}{run} \implies \cfrac{{\color{blue}{ y_2}}-{\color{blue}{ y_1}}}{{\color{red}{ x_2}}-{\color{red}{ x_1}}}
\\ \quad \\

y-{\color{blue}{ y_1}}={\color{green}{ m}}(x-{\color{red}{ x_1}})\qquad \textit{plug in the values and solve for "y"}\\
\qquad \uparrow\\
\textit{point-slope form} \)

Answer 3

So what? And can you help me with more?

Answer 4

well, find the slope
then plug the values in the point-slope form :)
then solve for "y"

Answer 5

I will medal, also are you in connexus?

Answer 6

I got the answer b.

Answer 7

what did you get for the slope?

Answer 8

-4

Answer 9

Never mind I'll gues can we do another?

Answer 10

Can you tell me if Im right?

Answer 11

well... you can always post anew

\(\bf \bf \begin{array}{lllll}
&x_1&y_1&x_2&y_2\\
&({\color{red}{ -1}}\quad ,&{\color{blue}{ -4}})\quad &({\color{red}{ 1}}\quad ,&{\color{blue}{ 4}})
\end{array}
\\\quad \\

slope = {\color{green}{ m}}= \cfrac{rise}{run} \implies \cfrac{{\color{blue}{ 4}}-{\color{blue}{ -4}}}{{\color{red}{ 1}}-{\color{red}{ -1}}}\implies \cfrac{8}{2}\implies 4\)

Answer 12

so now you know the slope, then just plug it in along with the point coordinates :)

Answer 13

Ok I got c now am I right?

Answer 14

well... try again.... notice the slope is 4
and the point you could use could be either point
so using the 1st point given

you'd end up with \(\bf y-{\color{blue}{ -4}}={\color{green}{ 4}}(x-{\color{red}{ -1}})
\)

Answer 15

Ok so 4y=4x-4 right?

Answer 16

well... \(\bf y-({\color{blue}{ -4}})={\color{green}{ 4}}(x-({\color{red}{ -1}}))\)

Answer 17

Now I think 4y=4x+1

Answer 18

Am I close now?

Answer 19

well... - * -4 = +4

Answer 20

\(\bf y-({\color{blue}{ -4}})={\color{green}{ 4}}(x-({\color{red}{ -1}}))\implies y+4=4(x+1)
\\ \quad \\
\implies y+4=4x+4\implies y=4x+4-4\implies y=4x\)

Answer 21

Your very good at this, can I ask one more. It was very clear and explained

Answer 22

ok

Answer 23

Which of the following equations would graph a line parallel to 3x-y=7?
a. y=7x-3
b. y=-3x+7
c. y=-7x + 3
d. y=3x

Answer 24

well if you solve -> 3x-y=7 <- for "y" what would it look like?

Answer 25

not a clue but I think 4x=-y

Answer 26

try adding "y" from both sides, then subtracting "7" to both sides

what would that give you?

Answer 27

So far 3x=7y is this correct?

Answer 28

well... \(\bf 3x-y=7\qquad {\color{red}{ +y}}
\\ \quad \\
3x\cancel{+y-y}=7+y\implies 3x=7+y\qquad {\color{red}{ -7}}
\\ \quad \\
3x-7=\cancel{7}+y\cancel{-7}\)

Answer 29

Im sorry but I have did every thing and still have not got any of those answers

Answer 30

well. after solving for "y"
what did we end up with?

Answer 31

-1

Answer 32

And one time 4

Answer 33

wel... not quite.. notice -> \(\bf 3x-y=7\qquad {\color{red}{ +y}}
\\ \quad \\
3x\cancel{+y-y}=7+y\implies 3x=7+y\qquad {\color{red}{ -7}}
\\ \quad \\
3x-7=\cancel{7}+y\cancel{-7}\)

what's "y" equals to?