Bonsoir ,
A)
A = 13/3 - 1/15 × 10/7
A = 13/3 - 10/105
A = 455/105 - 10/105
A = 445/105
A = 89/21
B ) 2a² - 5 = 1 + 3a
2a² - 3a = 1 + 5
a (2a - 3 ) = 6
a = 6 / (2a-3)
a = 2a - 2
a - 2a = -2
-a = -2
a = 2
C) PGCD (2574,1386) = 18
2574 ÷ 18 / 1368 ÷ 18 = 143/76
D) (5x-6)² - (x+2) (4x+6)
(5x)² + 6² - 2 × 5x × 6 - ( 4x² + 6x + 8x + 12 )
25x² + 36 - 60x - 4x² - 14x + 12
21x² - 74x + 48
E)
15x + 6 = -4x + 8
15x + 4x = 8 - 6
19x = 2
x = 2/19
4b + 5 - b + 3 = 4
3b = 4 - 5 - 3
3b = -4
b = -4/3