Question

ПОМОГИТЕ ПОЖАЛУЙСТА!!!
31.5. Вычислите с помощью формулы
a ^ 2 - b ^ 2 = (a - b)(a + b) ​

Answer 1

Ответ:

$13 {}^{2} - 9 {}^{2} = (13 - 9) \times (13 + 9) = 4 \times 22 = 88$

$20 {}^{2} - 19 {}^{2} = (20 - 19) \times (20 + 19) = 1 \times 39 = 39$

$2.2 {}^{2} - 2.8 {}^{2} = (2.2 - 2.8) \times (2.2 + 2.8) = ( - 0.6) \times5 = - 3$

$3.5 {}^{2} - 3.7 {}^{2} = (3.5 - 3.7) \times (3.5 + 3.7) = ( - 0.2) \times 7.2 = - 1.44$

$( \frac{5}{6} ) {}^{2} - ( \frac{2}{3}) {}^{2} = ( \frac{5}{6} - \frac{2}{3}) \times ( \frac{5}{6} + \frac{2}{3} ) = ( \frac{5}{6} - \frac{4}{6} ) \times ( \frac{5}{6} + \frac{4}{6} ) = \frac{1}{6} \times \frac{9}{6} = \frac{1}{6} \times \frac{3}{2} = \frac{1}{2} \times \frac{1}{2} = \frac{1}{4}$