If y varies inversely as x, and y = 1 as x = -2, how do you find y for the x-value of -1?

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Answer 1 · 2016-06-16T17:57:52

$y=2.$

Given that $yprop1/x.$
$:. y=k/x,$ , or, $xy=k$ ...(1), where $k!=0$ is constant of variation.

To determine $k,$ we use the given cond. that, $x=-2rArry=1.$

By (1) then, $k=-2.$ Hence (1) $rArr xy=-2.$ ...(2)

Now, when $x=-1, y=?$

(2) $rArr (-1)y=-2,$ or $y=2.$

Answer 2 · 2016-06-16T18:00:39

$y =2$

This is an example of inverse proportion, or inverse variation.

To change a proportion into an equation, multiply by a constant and then use the values given to find the value of the constant.

$y = k/x rArr k = xy$

$k= -2 xx 1 = -2$

So, $y = (-2)/x$

When $x = -1, " " y = (-2)/(-1)$