Question

kFind an equation for the line perpendicular to 4x+40y=360and goes through the point (-1,9 ).
Write your answer in the form y=mx+b .

Answer 1

divide through the equation by 40. we want to isolate or solve for y because we need to put it in slope intercept form (y=mx+b)

Answer 2

i did and i got y=4/40x+9 and i reduce it and got y=1/10x+9

Answer 3

i think you may have overlooked a negative sign. can you see that?

Answer 4

yes. so it will be y=-1/10x-9

Answer 5

close. the 9 stays pos.

Answer 6

so you get y=-1/10 x+9.

Answer 7

then i use that slope to find the equation for this points (-1,9)

Answer 8

yes. so what is the slope and what is the slope of the perpendicular line?

Answer 9

so it would be y=-1/10x+8

Answer 10

the first line has the equation y=-1/10x+9

Answer 11

now what do you think the slope of that line is?

Answer 12

positive 1/10

Answer 13

because from that slope, we us the rule that two lines that are perpendicular have slopes that are negative reciprocals of eachother.

Answer 14

you are close.

Answer 15

the slope is actually -1/10

Answer 16

y=-1/10x+8

Answer 17

whatever the number is in front of the x, that is the slope in slope intercept form

Answer 18

we know that the slope of the original line is-1/10, so what is the slope of the perpendicular line?

Answer 19

10/1

Answer 20

nice. absolutely correct.

Answer 21

so now, you can substitute the coordinates (-1,9) into the equation y=mx+b.

Answer 22

you should e getting something like 9=10(-1)+b.

Answer 23

solving for b gives b=20. so your equation is y=10x+20

Answer 24

so it would be y=10x+1

Answer 25

in order to solve 9=10(-1)+b, you get 9=-10+b; then add 10 to both sides of the equation to get b=20. so your equation is y=10x+20

Answer 26

feel free to ask a question if something is unclear.

Answer 27

i get it. thanks

Answer 28

no problem. take care

Answer 29

you to