Explications étape par étape:
a.
= (5×6)x - (5×7)x + 8x - 2x×x
= 30x - 35x + 8x - 2x²
= -2x² + 3x
b.
= (7×3)x² - (2×7)x - (2×(-6))x - 2x²
= 21x² - 14x + 12x - 2x²
= 19x² - 2x
c.
= 10 - 4x - 8x - 10x²
= -10x² - 12x + 10
d.
= -4x - 12 + 30 + 5x
= x + 18
etc...