SOLUTION: y varies directly with x. If y is -32 when x is 4, find x when y is -40

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Question 928960: y varies directly with x. If y is -32 when x is 4, find x when y is -40
Answer by MathLover1(20849) About Me  (Show Source):
You can put this solution on YOUR website!

if y varies directly with x, then there is a constant k such that y=k%2Ax

if y=-32 when x=4, we can find the constant k
-32=k%2A4
-32%2F4=k
k=-8 and our function is y=-8x
so, to find x when y=-40 just plug known variable in y=-8x
-40=-8x...solve for x
-40%2F-8=x
x=40%2F8
x=5