bonjour
A = 8/7 + 20/21
= 24/21 + 20/21
= 44/21
B = - 3 : ( 4/2 + 5/2)
= - 3 : 9/2
= - 3 * 2/9
- 6 /9 = - 2/3
C = ( - 6/9 + 4 /9 ) x 7/16
= - 2 /9 x 7/16
= - 14 / 144 = - 7 / 72
A = 246 x 10 ⁵ x 10 ⁻¹⁰
= 246 x 10 ⁻⁵
= 0.00 246
= 2.46 x 10 ⁻³
B = 800 + 0.85 = 800.85
= 8.0085 x 10 ²
C = 21 x 10 ⁶ : 50 x 10 ⁻⁴
= 0.42 x 10 ¹⁰
= 4.2 x 10 ⁹
départ 1 bactérie
au bout de 30 min = 2
au bout d'1 h = 2 ²
2 h = 2 ⁴
3 h = 2 ⁶
etc...
