Bonjour,
Calcule les expressions suivantes lorsque a= 2/3 ; b= - 3/2 ; c= - 3/4.
A)=3a-b-c.
3 * 2/3 - (- 3/2) - (- 3/4)
= 6/3 + 3/2 + 3/4
= 24/23 + 18/12 + 9/12
= 51/12
= 17/4
B)-2a+4b-5c.
- 2 * 2/3 + 4 * - 3/2 - 5 * - 3/4
= - 4/3 - 12/2 + 15/4
= - 16/12 - 72/12 + 45/12
= - 43/12
C)6b²-3a+5.
6 * (- 3/2)² - 3 * 2/3 + 5
= 6 * - 3²/2² - 6/3 + 5
= 6 * 9/4 - 6/3 + 5
= 54/4 - 2 + 5
= 13,5 + 3
= 16,5
D)1/a+ 1/b+1/c.
1 : 2/3 + 1 : - 3/2 + 1 : - 3/4
= 1 x 3/2 + 1 x - 2/3 + 1 x - 4/3
= 3/2 - 2/3 - 4/3
= 9/6 - 4/6 - 8/6
= - 3/6
= - 1/2
E)a+c/a-b
2/3 + (- 3/4) : 2/3 - (- 3/2)
= 2/3 - 3/4 x 3/2 + 3/2
= 2/3 - 9/8 + 3/2
= 16/24 - 27/24 + 36/24
= 25/24.
