Sagot :
bonjour
E = (2x+3)(x+5)-(2x+3)(3x+2)
E = 2 x² + 10 x + 3 x +15 - ( 6 x² + 4 x + 9 x + 6 )
E = 2 x² + 13 x + 15 - 6 x² - 13 x - 6
E = - 4 x² + 9
E = ( 2 x + 3 ) ( x + 5 - 3 x - 2 )
E = ( 2 x + 3 ) ( - 2 x + 3 )
Bjr
1) Développer et réduire :
E = (2x+3)(x+5)-(2x+3)(3x+2)
E = (2x+3)(x+5-(3x+2))
E = (3+2x)(x+5-(3x+2))
E = (3+2x)(x+5-3x-2)
E = (3+2x)(-2x+5-2)
E = (3+2x)(-2x+3)
E = (3+2x)(3-2x)
Identité remarquable → (a-b)(a+b) = a²-b²
E = -4x²+9
2) Factoriser :
E = (2x+3)(x+5)-(2x+3)(3x+2)
E = (2x+3)(x+5-(3x+2))
E = (2x+3)(x+5-3x-2)
E = (2x+3)(-2x+5-2)
E = (2x+3)(-2x+3)
Voilà !