If y varies directly with x, and If y = 4 when x = 12, how do you find y when x = -24?

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Answer 1 · 2016-03-08T02:23:06

#y=-8#

If #y# varies directly with #x#, an equation to express this can be:

#y=mx#

#1#. Since #y=4# when #x=12#, substitute the values into #y=mx# to determine the value of #m#.

#y=mx#

#4=m(12)#

#color(blue)(m=1/3)#

#2#. With the value of #color(blue)m# known, substitute #color(blue)m# and #x=-24# into #y=mx# to determine the value of #y#.

#y=color(blue)(1/3)x#

#y=color(blue)(1/3)(-24)#

#y=1/color(red)cancelcolor(black)(3)^1(-color(red)cancelcolor(black)(24)^8)#

#color(green)(y=-8)#

#:.#, #y=-8# when #x=-24#.