Given y varies directly with x, write the equation of the line when x=3 and y=-12?

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Answer 1 · 2016-11-20T21:49:21

$y = - 4 x$ $y = -4x$

If y and x are in direct proportion, then they are linked by a constant.

$y \propto x \leftarrow$ $ypropx" "larr$ write the proportion

$y = k x \leftarrow$ $y = kx" "larr$ make an equation with a constant

$\frac{y}{x} = k$ $y/x = k$

$- \frac{12}{3} = k \leftarrow$ $-12/3 = k" "larr$ use the given values to find k.

$k = - 4$ $k = -4$

Now we can write an equation:

$y = - 4 x$ $y = -4x$