Bonjour,

Question 1 :

f(x) = x² + 1

f'(x) = 2x

Question 2 :

f(2) = 2² + 1 = 4 + 1 = 5

f'(2) = 2 × 2 = 4

y = f'(a)(x - a) + f(a)

 ⇔ 4(x - 2) + 5

 ⇔ 4x - 8 + 5

 ⇔ 4x - 3