If y varies directly with x, if y = 8 as x = -4 how do you find the direct variation equation?

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Answer 1 · 2016-08-22T17:45:18

#y+2x=0#

#8=-4k#

or

#k=constant=-8/4=-2#

Therefore we can write #y=-2x#

or

#y+2x=0#

Answer 2 · 2016-08-22T17:51:13

#x = -2y#

Write the given information in Maths first.

#x prop y" values which are in proportion to each"#
#color(white)(xxxxxxxxx)"other are connected by a constant."#

#color(red)(x = ky) color(white)(xxxxxxxxxxxx)" make an equation using k"#

#k = x/y = -4/8 = -2 color(white)(xxxxxxxxx) "find a value for k"#

Now put the value for 'k' into the equation.

#color(red)(x = -2y)#