Bonjour
Soit f(x) = (2x + 5)(x + 1) + 3(x + 1)
1) Développer et réduire f(x).
f(x) = (2x + 5)(x + 1) + 3(x + 1)
f (x) = 2x² + 2x + 5x + 5 + 3x + 3
f (x) = 2x² + 10x + 8
2) Factoriser f(x).
f(x) = (2x + 5)(x + 1) + 3(x + 1)
f (x) = (x + 1) (2x + 5 + 3)
f (x) = (x + 1) (2x + 8)
f (x) = 2 (x + 1) (x + 4)
3) Calculer f(-1) et f(1 sur 2).
f (x) = 2x² + 10x + 8
f (- 1) = 2 * (- 1)² + 10 * (- 1) + 8
f (- 1) = 2 * 1 - 10 + 8
f (- 1) = 2 - 2
f (- 1) = 0
f (x) = 2x² + 10x + 8
f (1/2) = 2 * (1/2)² + 10 * (1/2) + 8
f (1/2) = 2 * 1²/2² + 10/2 + 8
f (1/2) = 2 * 1/4 + 5 + 8
f (1/2) = 2/4 + 5 + 8
f (1/2 = 1/2 + 13
f (1/2 = 13,5.
