Bonjour, quelqu'un pourrait il m'aider ?

exo 6 :
1°)   B = 5 ( 7 - 3b ) - b² + b ( 2b - 12 ) = 35 - 15b - b² + 2b² - 12b
                                                             = b² - 27b + 35
       3 C = 5 ( 2a + 7 ) + 7 ( 2a/11 - 4 ) = 10a + 35 + 14a/11 - 28
             = (10 + 14/11) a + 7 = (110/11 + 14/11) a + 7 = 124a/11 + 7
      donc C = 124a/33 + 7/3
2°) C = 8 (3a-8) - 5a (3a-8) = (3a-8) (8-5a)
3°) A = 3 * (-3)² + 5 * (-3) - 8 = 3 * 9 - 15 - 8 = 27 - 23 = 4
4°) 2 a² - 2a (a-8) = 13 donne 2 a² - 2 a² + 16a = 13 donc a = 13/16

bonjour
1/a: 5(a-7)-(6a-8)=
5a-35-6a+8=
-a-27

b:-5(3b-7)-b²+b(2b-12)=
-15b+35-b²+2b²-12b=
b²-27b+35

c:5/3(2a+7)-7/3(4-2/11a)=
10/3*a+35/3-26/3-14/33*a=
124/33*a+7/3

2/factoriser
a 15+5a
5*3=15
5*a=5a
5(3*a)
b a²-17a
a*a=a²
a*(-17)=-17a
a(a-17)
c8(3a-8)-5a(3a-8)=
(3a-8)(8-5a)

3/ a =3a²+5a-8=3*(-3)²+5*(-3)-8=4
b (8a+1)(a-6)=(8*(-3)+1)(-3-6)=207

4/ 3a-7=5
3a=5+7
3a=12
a=12/3=4

14a+6=-7
14a=-7-6
14a=-13
a=-13/14

2a²-2a(a-8)=13
2a²-2a²+16a=13
16a=13
a=13/16