a = [tex]\sqrt{\frac{4d}{bc} }[/tex]
isolate the term in a
[tex]\frac{1}{4}[/tex] a²bc = d ( multiply both sides by 4 to eliminate the fraction )
a²bc = 4d ( divide both sides by bc )
a² = [tex]\frac{4d}{bc}[/tex]
Take the square root of both sides
a = [tex]\sqrt{\frac{4d}{bc} }[/tex]