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)
