Ответ:

[tex] \sqrt{ {1.53}^{2} - {0.72}^{2} } = \sqrt{(1.53 - 0.72)(1.53 + 0.72)} = \sqrt{0.81 \times 2.25} = \sqrt{ \frac{81}{100} \times \frac{225}{100} } = \sqrt{ \frac{81}{100} } \times \sqrt{ \frac{225}{100} } = \frac{9}{10} \times \frac{15}{10} = \frac{27}{20} = 1 \times \frac{7}{20} [/tex]