What is the length of x? Simplify the radical if necessary.?

Question

Krishnamurthy · Answer

x = sqrt(21^2 - 15^2) = sqrt(36*6) = 6 sqrt 6
Answer: B

? · Answer

// According to the Pythagorean Theorem
x² + 15² = 21²
x² = 21² - 15²x² = 216

x = √216 = 6√6 ............ANS (Option B)

llaffer · Answer

Since this is a right triangle we can use Pythagorean Theorem to find the unknown:

a² + b² = c²
x² + 15² = 21²
x² + 225 = 441
x² = 216
x = √216
x = √(4 * 9 * 6)
x = 2 * 3√6
x = 6√6 units (answer B)

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