bonjour
a) (x+3) (x+5)-4x
= x² + 5 x + 3 x + 15 - 4 x
= x² + 4 x + 15
b)x(3-2x)+5x²
= 3 x - 2 x² + 5 x²
= 3 x² + 3 x
c) (5-t) (1+2t)+2(3t+4)
= 5 + 10 t - t - 2 t² + 6 t + 8
= - 2 t² + 15 t + 13
d)2x²(x+6)-x³+4x²-2x
= 2 x ³ + 12 x² - x ³ + 4 x² - 2 x
= x ³ + 16 x² - 2 x
