Question

What is the equation of the line perpendicular to –x + y = 7 and passing through (-1, -1)?

Answer 1

-x + y = 2
-x – y = 2
x – y = 2
-x – y = 0
x + y = 0

are the answer choices...can anyone help explain how i can solve this please?

Answer 2

First, you need to determine the slope of the given equation.

Answer 3

and the slope is (7,1) ?

Answer 4

@Redcan ?

Answer 5

\[y=x+7\] So comparing with the slope intercept form of the line, \[y=mx+b\] we see the slope is 1.

Answer 6

ohhh ok right, so with a slope of 1, do i have to plug that into the answer choices?

Answer 7

You want a line perpendicular to a line with slope one. So you need a line with new slope of -1/m.

Answer 8

Draw a sketch and convince yourself.

Answer 9

and perpendicular is creating a 90 degree angle right?

Answer 10

yep

Answer 11

Now use the point slope form of the line to find a line with slope -1 through (-1,-1).

Answer 12

i dont think im drawing this correctly lol...ok so, on my graph i need to draw the first line, which is (-1,-1)

Answer 13

and then the second line, has to create a 90 degree angle passing through the (-1,-1)?

Answer 14

\[y-y_0=(x-x_0)m = (y-(-1))=(x-(-1))(-1)\]

Answer 15

im trying to understand :( i just cant get it

Answer 16

(-1,-1) is a point. y=mx+b is a line where m is slope.

Answer 17

but i've gtg. sry

Answer 18

@devmarie: Could you possibly explain what it is that you do understand here, as well as what you don't?

What have you done so far towards solving this problem?

Hint: Solve -x + y = 7 for y. Determine the slope of this straight line.