Svppppppppppppppppppppp Le 68 merci

1) C= 4B=4*(6+5t) 
      =24+20t
D=-3A = -3* (7-4t)
   = -21 +12t
E= A+B= (7-4t) + ( 6+5t)
  = 13 + t
F = A-B= ( 7-4t) - ( 6+5t) 
   =  1-9t 
G = 4B - 3A = 4 (6+5t) - 3 (7-4t)
   = 24 + 20t -21 - 12t
  = 3+8t
H= AB= (7-4t) (6+5t)
   = 42+35t-24t -20t^2
= -20t^2 +11t +42

2) 5A+4B -59=
= 5* ( 7-4t) +4(6+5t) -59
= 35 - 20t +24 +20t -59
=59-59=0