If y varies directly with x and y = -7 when x = -1, find x when y = -84.
Answer

84

7

-12

Question

If y varies directly with x and y = -7 when x = -1, find x when y = -84.
Answer
		
84
		
7
		
-12

phi · Answer

can you find k ?  in
y = k x

anonymous · Answer

how do you find k

phi · Answer

use  y = -7 when x = -1,
in 
y = k x
that means replace y with -7  and x with -1
what do you get ?

jdoe0001 · Answer

anonymous · Answer

-7=k*-1

phi · Answer

now divide both sides by -1.  on the right side -1 divided by -1 is 1

phi · Answer

$$ \frac{-7}{-1}= \frac{-1}{-1} k $$

anonymous · Answer

ok so -7=k*1

phi · Answer

almost.  -7 divided by -1 is +7  (two minus signs make a positive)

anonymous · Answer

oh my calculator didnt take away the negetive
ok i get it now

phi · Answer

you now know k= 7
so your equation y= k x is now
y = 7 x  

now if you want y for some x, replace x with the number, and multiply it by 7

phi · Answer

or in this case, replace y with -84

anonymous · Answer

i am confused

phi · Answer

do you understand how we got
y = 7 x 
?

anonymous · Answer

yes

anonymous · Answer

the answer is 7!

phi · Answer

they say y = -84.
in
y = 7 x
replace y with -84
-84 = 7 x

to find x, divide both sides by 7
-84/7  = x

I don't think that is 7