exercice 1 svp :( 1/4+3/4:(1+1/8) 2-3/4x9/21 2x10(5)x(3x10(3))(2)

1/4 + 3/4 / (1 +1/8)
4/4 /( 8/8 +1/8)
4/4 / 9/8= 4/4 X 8/9 = 32/36 = 16/18 = 8/9

2 - 3/4 X 9/21
2 -27/ 84
48/84 -27/84 = 21/84 = 7/28 = 1/4

2 X 10⁵ X (3 X 10⁻³)²  = 2 X 10⁵ X 3 X 10⁹  = 6 X 10⁵⁺⁹ = 6 X 10¹⁴⁻² = 0,4 X 10¹²
15 X 10²                      15 X 10²                  15 X 10²     15