The variables x=9 and y=15 varies directly. How do you write an equation that relates the variables and find x when y=-5?

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The variables x=9 and y=15 varies directly. How do you write an equation that relates the variables and find x when y=-5?

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Answer 1 · 2017-09-28T23:33:28

$x=3$ when $y=5$

Explanation:

When y increases, x also increases in the same proportion and when y decreases, x also decreases in the same proportion.
So $x:y=x1:y1$
Or $x/y=(x1)/(y1)$
We know, y=15, x=9 and y1=5
$:.x1=((x/y)(y1)=(9/15)5=45/15=3$
$x1=3$

Answer 2 · 2017-09-28T23:47:34

The equation is $y=5/3x$
and
$y=-5color(white)("xx")rarrcolor(white)("xx")x=-3$

Explanation:

If $x$ and $y$ vary directly, then
$color(white)("XXX")y=color(blue)c * x$ for some constant $color(blue)c$

Given that $x=9$ and $y=15$ is one solution to this equation:
$color(white)("XXX")15=color(blue)c * 9$

$color(white)("XXX")rarr color(blue)c=15/9=color(blue)(5/3)$

So the relating equation is $y=color(blue)(5/3)x$

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

When $y=-5$ , the equation becomes:
$color(white)("XXX")-5=color(blue)(5/3)color(green)x$

$color(white)("XXX")rarr color(green)x=(-5)xx3/5)=color(green)(-3)$

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The variables x=9 and y=15 varies directly. How do you write an equation that relates the variables and find x when y=-5?

2 Answers

Explanation:

Explanation:

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