Bonjour,
Factoriser dans la série 2 les expressions:
25x²-(2x+3)²= (5x-2x-3)(5x+2x+3)= (3x-3)(7x+3)= 3(x-1)(7x+3)
-4x²-20x-25= - (2x+5)²
x^4-81y^4= (x-3y)(x+3y)(x²+9y²)= (x²-9y²)(x²+9y²)
(5x+3)(3x-5)+(x+3)(-5+3x)= (3x-5)(5x+3+x+3)= (3x-5)(6x+6)= 6(3x-5)(x+1)
16x²+1/9= 1/9( 144x²+1)
