Question

if y=4 when x=-2, find x when y=6

Answer 1

-2/4 =x/6
-2x=24
x=?

Answer 2

x=-3

Answer 3

24/-2=-12

Answer 4

dont you multiply criss cross ways

Answer 5

Wait... you're right because i set it up wrong

Answer 6

Mmhmm. You were right. It was supposed to be -12=4x

Answer 7

y varies directly as xsquared : If y =15 when x=5 , find y when x =10

Answer 8

are u still there

Answer 9

y varies directly as xsquared : If y =15 when x=5 , find y when x =10

Answer 10

im here sorry i's hectic over here

Answer 11

yx^2=k, right?
15(25)=k
375=k
So then 375=y10^2
375=100y
y=3.75

Answer 12

Double check?

Answer 13

huh

Answer 14

\When two variables vary directly, it means they're multiplied and equal k (constant)

Answer 15

So y times x^2 equals k
We plug in the numbers
(15)(5^2)=k
(15)(25)=k
k=375

Answer 16

Good so far?

Answer 17

what about the find y when x =10

Answer 18

y varies inversely as x: If x=8 when y=9 , find x when y=18

Answer 19

When y equals ten, you plug y and k back into the original equation, so 10^2y=375
y=3.75

Answer 20

WAIT NO TAT's BACKWARDS

Answer 21

15/25=k
.6=k

Answer 22

100y=.6
y=.006

Answer 23

So inversely means multiplied. 9(8)=k
k=72
18x=72
x=4

Answer 24

im lost

Answer 25

Okay, where did I lose you?

Answer 26

ithought that i would multiply the 8 x 18 and the 9 and x together

Answer 27

Any variation equals a constant. So xy=k or x/y=k or x/yz=k

Answer 28

Directly means divide, so x/y=k
What were the variables again?

Answer 29

x=8 when y =9, find x when y=18

Answer 30

Okay, an this is inversely, right? So xy=k
You plug in x and y and get (8)(9)=k
72=k

Answer 31

Now that you have the constant, you plug it back into the original equation. xy=72

Answer 32

You also have y now, so plug that in too for 18x=72
Now solve.
x=72/18
x=4

Answer 33

so y=4

Answer 34

Close. y was 18, so x is 4

Answer 35

if x=2 when y=10, find y when x=4

Answer 36

how do they vary?

Answer 37

oh, i got it. sorry. Okay, so 2/10=4/y
40=2y
y=?

Answer 38

xy=k
2(10)=k
k=20
4y=20
y=5

Answer 39

Yeah you were right. Sorry, i tried to set it up in fractions.