Question

daca x<0,calculati $\sqrt{9x^{2} } .$
Calculati $\sqrt{ {5}^{2} - {4}^{2} } .$

Answer 1

$\it \sqrt{9x^{2} } = \sqrt{(3 \cdot |x| )^{2} } = 3 \cdot |x| = - 3x. \\ \\ \it \sqrt{ {5}^{2} - {4}^{2} } = \sqrt{25 - 16} = \sqrt{9} = 3.$