Bonsoir,
A = (3t - 2)^2 - (3t - 2)(t + 4)
1) développer :
A = 9t^2 - 12t + 4 - (3t^2 + 12t - 2t - 8)
A = 9t^2 - 12t + 4 - 3t^2 - 10t + 8
A = 6t^2 - 22t + 12
2) factoriser :
A = (3t - 2)(3t - 2 - t - 4)
A = (3t - 2)(2t - 6)
A = 2(3t - 2)(t - 3)
3) a) t = 0
A = 6 * 0^2 - 22 * 0 + 12
A = 12
b) t = -1
A = 2(3 * (-1) - 2)(-1 - 3)
A = 2(-3 - 2) * (-4)
A = (-8) * (-5)
A = 40