Question

what is a slope of a line perpendicular to the line with equation y=4x+5

Answer 1

any ideas?

Answer 2

would i have to solve the equation? i don't know how to do this :(

Answer 3

no, no need to solve

do you know how to find the slope of y = 4x + 5?

Answer 4

slope intercept form?

Answer 5

good, but it's already in slope intercept form

Answer 6

so the slope is 4

Answer 7

good!

now, to find the perpendicular slope, you turn 4 into 1/4 (by taking the reciprocal) and multiply it by -1 to get -1/4

Answer 8

so -1/4 is your answer

Answer 9

would you do the same for parallel?

Answer 10

for parallel, you just leave the slope alone

Answer 11

(since parallel lines have equal slopes)

Answer 12

so for parallel it would be 4

Answer 13

what if it is not in slope intercept form?

Answer 14

change it into intercept form

Answer 15

would you like an example?

Answer 16

yes please

Answer 17

ok, say we have

-2x + y = 3

Answer 18

do you know how we could change it to y = mx + b form?

Answer 19

by isolating y?

Answer 20

yes!

Answer 21

would you like to try giving it a go?

Answer 22

yeah gimme a sec

Answer 23

so i subtracted 2x from both sides and i got y = 3 - 2x

Answer 24

@Vocaloid

Answer 25

almost

Answer 26

instead of subtracting, you actually want to add 2x instead

Answer 27

but 2x wasn't negative?

Answer 28

since we had -2x initially, we must add 2x to get 0

Answer 29

our original problem was - 2x + y = 3 so yes, x was negative

Answer 30

oh i didn't see the negative sorry

Answer 31

nah it's cool

Answer 32

so that gives us y = 3 + 2x. we can just switch the 3 and 2x to get
y = 2x + 3

Answer 33

making our slope 2 (parallel) and -1/2 (perpendicular)

Answer 34

oh okay!

Answer 35

thank u!