1) Combien y-a-t-il d'élèves en 4e A ? 3/4 x 5/6 = 15/24 = 3 x 5 / 3 x 8 = 5/8 Soit le nombre d'élèves de la 4e A 5/8x = 15 x = 15 * 8/5 x = 120/5 x = 24 24 élèves sont en 4eA
6) Pour a = - 2/3
A = (a + 2) (a - 2) A = (- 2/3 + 2) (2/3 - 2) A = (- 2/3 + 6/3) (2/3 - 6/3) A = 4/3 * - 4/3 A = - 16/9
B = 2 - 1/a B = 2 - 1- 2/3 B = 2 - 1 x - 3/2 B = 2 + 3/2 B = 4/2 + 3/2 B = 7/2
C = a__ a + 2 C = 2/3 2/3 + 2 C = 2/3 2/3 + 6/3 C = 2/3 : 8/3 C = 2/3 x 3/8 C = 6/24 C = 6 x 1 / 6 x 4 C = 1/4
D = (2a - 1) (2a + 1) D = (2 * - 2/3 - 1) (2 * - 2/3 + 1) D = (- 4/3 - 1) (- 4/3 + 1) D = (- 4/3 - 3/3) (- 4/3 + 3/3) D = - 7/3 * - 1/3 D = 7/9
E = (1/a + 1) (1/a - 1) E = (1 : - 2/3 + 1) (1 : - 2/3 - 1) E = (1 x - 3/2 + 1) (1 x - 3/2 - 1) E = (- 3/2 + 2/2) (- 3/2 - 2/2) E = - 1/2 * - 5/2 E = 5/4
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Verified answer
1) Combien y-a-t-il d'élèves en 4e A ?3/4 x 5/6 = 15/24 = 3 x 5 / 3 x 8 = 5/8
Soit le nombre d'élèves de la 4e A
5/8x = 15
x = 15 * 8/5
x = 120/5
x = 24
24 élèves sont en 4eA
6)
Pour a = - 2/3
A = (a + 2) (a - 2)
A = (- 2/3 + 2) (2/3 - 2)
A = (- 2/3 + 6/3) (2/3 - 6/3)
A = 4/3 * - 4/3
A = - 16/9
B = 2 - 1/a
B = 2 - 1- 2/3
B = 2 - 1 x - 3/2
B = 2 + 3/2
B = 4/2 + 3/2
B = 7/2
C = a__
a + 2
C = 2/3
2/3 + 2
C = 2/3
2/3 + 6/3
C = 2/3 : 8/3
C = 2/3 x 3/8
C = 6/24
C = 6 x 1 / 6 x 4
C = 1/4
D = (2a - 1) (2a + 1)
D = (2 * - 2/3 - 1) (2 * - 2/3 + 1)
D = (- 4/3 - 1) (- 4/3 + 1)
D = (- 4/3 - 3/3) (- 4/3 + 3/3)
D = - 7/3 * - 1/3
D = 7/9
E = (1/a + 1) (1/a - 1)
E = (1 : - 2/3 + 1) (1 : - 2/3 - 1)
E = (1 x - 3/2 + 1) (1 x - 3/2 - 1)
E = (- 3/2 + 2/2) (- 3/2 - 2/2)
E = - 1/2 * - 5/2
E = 5/4