5)(ab+ba/a + b)² x ab = 1573
(10 a + b + 10b + a/a + b)² x ab = 1573
(11a + 11b/a + b,simplficam cu a + b) x ab = 1573
11² x ab = 1573
121 x ab = 1573
ab = 1573 : 121 = 13
6) 2ˣ + 2ˣ⁺¹ = 48
2(2ˣ⁻¹ + 2ˣ) = 2 x 24
2ˣ⁻¹ + 2ˣ = 24
2(2ˣ⁻² + 2ˣ⁻¹) = 2 x 12
2ˣ⁻² + 2ˣ⁻¹ = 12
2(2ˣ⁻³ + 2ˣ⁻²) = 2 x 6
2ˣ⁻³ + 2ˣ⁻² = 6
2(2ˣ⁻⁴ + 2ˣ⁻³) = 2 x 3
2ˣ⁻⁴ + 2ˣ⁻³ = 3
=> x = 4
