SOLUTION: Write a formula that expresses the relationship described below y varies directly as x and y = –10 when x = –7. What are the key words that I should notice that helps me writ

Algebra ->  Equations -> SOLUTION: Write a formula that expresses the relationship described below y varies directly as x and y = –10 when x = –7. What are the key words that I should notice that helps me writ      Log On


   

Question 150793: Write a formula that expresses the relationship described below
y varies directly as x and y = –10 when x = –7.

What are the key words that I should notice that helps me write formulas?....I know y = ?/?
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
A direct variance means that as x increases y increases. Also as x decreases y decreases . So this is reflected by the equation y=kx


y=kx Start with the given equation.


-10=k%28-7%29 Plug in x=-7 and y=-10.


-10=-7k Rearrange the terms


%28-10%29%2F%28-7%29=k Divide both sides by -7.


10%2F7=k Reduce


k=10%2F7 Rearrange the equation


So the equation is y=%2810%2F7%29x