Sagot :
Bonsoir,
On a :
A = 7x(x+2) + (2x-1)(3x-5)
A = 7x² + 14x + (6x² - 10x - 3x + 5)
A = 7x² + 14x + 6x² - 13x + 5
A = 13x² + x + 5
B = (7x+3)²
B = 49x² + 42x + 9
C = (4x-1)(4x+1) - (x-5)²
C = (16x² - 1) - (x² - 10x + 25)
C = 16x² - 1 - x² + 10x - 25
C = 15x² + 10x - 26
Réponse:
A= 7x(x+2)+(2x-1)(3x-5)
=( 7x²+ 14x)+ (6x²-10x-3x+5)
=7x²+14x+6x²-13x+5
= 7x²+6x²+14x-13x+5
= 13x²+x+5
B= (7x+3)²
identité remarquable
(a+b)²= a²+2ab+b²
= (7x)²+2× 7x × 3+ 3²
= 49x²+ 42x+9
C= (4x-1)(4x+1)-(x-5)²
identité remarquable (a+b)(a-b)= a²-b²
et
(a-b)²= a²-2ab+b²
= 16x²-1-(x²-2×x×5+5²)
=16x²-1-(x²-10x+25)
= 16x²-1-x²+10x-25
=15x²+10x-26