- 6 Développer les expressions suivantes : a) (x + 5)(x – 5) b) (3x +8)(3x - 8) c) (2t+3)(2t - 3). -

Bonsoir

Politesse !

Développer :

A = (x+5)(x-5)

A = x×x-5x+5x-5×5

A = x²-5x+5x-5×5

A = x²-5x+5x-25

A = x²-25

B = (3x+8)(3x-8)

B = 3x×3x-3x×8+8×3x-8×8

B = 9x²-3x×8+8×3x-8×8

B = 9x²-24x+8×3x-8×8

B = 9x²-24x+24x-8×8

B = 9x²-24x+24x-64

B = 9x²-64

C = (2t+3)(2t-3)

C = 2t×2t-2t×3+3×2t-3×3

C = 4t²-2t×3+3×2t-3×3

C = 4t²-6t+3×2t-3×3

C = 4t²-6t+6t-3×3

C = 4t²-6t+6t-9

C = 4t²-9

Bonne soirée.