#3u ^ { 2} - 5d \div 5= 0#
#3u^2-(5d)/5=0#
#color(red)("Simplifying:")#
#3u^2-d=0#
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#color(green)("SOLVING FOR 'd':")#
#color(red)("Rearrange equation to isolate d:")#
#therefore d=3u^2#
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#color(green)("SOLVING FOR 'u':")#
#3u^2=d#
#color(red)("Divide both sides by 3:")#
#u^2=d/3#
#color(red)("Take square root of both sides:")#
#therefore u=+-sqrt(d/3)#