Question

a 5 4 2 3 √17 √21

Explanation:

Step1: Apply Pythagorean theorem

For a right - triangle, \(c^{2}=a^{2}+b^{2}\), where \(c = 5\), \(b = 4\), and \(a\) is the unknown side. So \(a^{2}=c^{2}-b^{2}\).

Step2: Substitute values

Substitute \(c = 5\) and \(b = 4\) into the formula: \(a^{2}=5^{2}-4^{2}\).

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Step3: Solve for \(a\)

Take the square root of both sides: \(a=\sqrt{9}=3\) (we consider the non - negative value since \(a\) represents the length of a side of a triangle).

Answer:

3