1.

1)

(0,8⁻² + 0,6⁻²)⁻¹ = ( (8/10)⁻² + (6/10)⁻² )⁻¹ = ( (10/8)² + (10/6)² )⁻¹ =

= (100/64 + 100/36)⁻¹ = (900/576 + 1600/576)⁻¹ =

= (2500/576)⁻¹ = 576/2500 = 144/625 = 0,2304,

2)

(5 * 2⁻² - 20 * 5⁻²) : (4/3)⁻² = (5 * (1/2)² - 20 * (1/5)²) : (3/4)² =

= (5 * 1/4 - 20 * 1/25) : (9/16) = (5/4 - 20/25) * 16/9 =

= (125/100 - 80/100) * 16/9 = 45/100 * 16/9 = 4/5 = 0,8,