Find AB if BC = 4, BD = 5, and AD = 2.

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Solving this system of equations without a CAS: $4=a+c$, $5=d+ac+b$, $4=ad+bc$, $4=bd$ 2

Let $A, B, C, D$ be the vertices of a four sided polygon taken in anti clockwise. Given $|AB|=|BC|=3,|AD|=|CD|=4,|BD|=5$, Find $|AC|$ 1

Find $ad - bc$ if $ac = 18$ and $bd = 50$ 2