Bonjours, j'aurais besoin d'aide pour des exercices : 3/4 + 5/4 × 7/15 = 5/6 - 5/4 sur 5/8= 8×10¹⁵×15×10-⁶ sur 20×(10²)⁵= (Pour la dernière c'est...15×10 puiss

Bonsoir

3/4 + 5/4 × 7/15 =

= 3/4 + 5/15 x 7/4

= 3/4 + 5/(3 x 5) x 7/4

= 3/4 + 1/3 x 7/4

= 3/4 + 7/12

= (3 x 3)/(4 x 3) + 7/12

= 9/12 + 7/12

= 16/12

= (4 x 4)/(4 x 3)

= 4/3

5/6 - 5/4 sur 5/8=

= 5/6 - 5/4 x 8/5

= 5/6 - 5/5 x 8/4

= 5/6 - (2 x 4)/4

= 5/6 - 2

= 5/6 - (2 x 6)/6

= 5/6 - 12/6

= -7/6

8×10¹⁵×15×10-⁶ sur 20×(10²)⁵=

= (8 x 15 / 20) x 10^(15-6-2x5)

= (2 x 4 x 3 x 5)/(5 x 4) x 10^(9-10)

= 6 x 10^(-1)