For each card below, determine which non-negative values of \(a\), \(b\), \(c\), and \(d\), if any, make the equation true.
Have you tried substituting some numbers into the equations? This will give you a feeling for how the equation is behaving and may help you to decide what to do next.
Can you find equations that look familiar? Perhaps start here.
Can you sort the cards into pairs or groups of equations with similar properties?