Hello !
A = 5x - 6(-2x + 1)
= 5x - (-12x) - 6
= 17x - 6
B = 2(3x + 5)-4(x + 2)
= 6x + 10 - 4x - 8
= 2x - 2
C = 5 + (2x - 7)(4 - 3x)
= 5 + 8x - 6x² -28 + 21x
= -6x² + 29x - 23
D = 3 - (4x + 1)(-x + 2)
= 3 - (-4x² + 8x - x + 2)
= 3 + 4x² - 8x + x - 2
= 4x² - 7x + 1
E = 15x - (x + 7)²
= 15x - (x² + 14x + 49)
= 15x - x² - 14x - 49
= -x² + x - 49
Tu essayes de faire les 2 derniers ?