Ex 1
A = 16x²-81 = (4x+9)(4x-9)
B = (5x+3)(x-1)+(3x+4)(x-1)
= (x-1) * [(5x+3)+(3x+4)]
= (x-1)*(8x+7)
C = 25x²-(x+7)²
= (5x+x+7)(5x-x-7)
= (6x+7)(4x-7)
Ex 2
1) Faux 2 + 4/3 = 6/3 + 4/3 = 10/3
2) Faux (3√5)² = 3² * (√5)² = 9 * 5 = 45
3) Faux 10^5 + 10^-5 = 100000 + 0,00001 = 100000,00001
4) Vrai (n+2)² - (n-2)² = [(n+2)+(n-2)] * [(n+2)-(n-2)]
= (n+n+0) * (n-n+4)
= 2n * 4
= 8n
Quel que soit la valeur de n, 8n sera un multiple de 8
5)Faux (3+√2)² = 3² + 2*3*√2 + (√2)² = 9 + 6√2 + 2 = 11 +6√2
