developper, reduire et ordonner les expression a = (x+3) (x-5) b = 3(x - 10) - (x+2) (-x + 5) c = (3x + 5)²

a = ( x + 3 ) ( x - 5 )
= x * x + x * (-5) + 3 * x + 3 * (-5)
= x^2 - 5x + 3x - 15
= x^2 - 2x - 15

b = 3 ( x - 10 ) - ( x + 2 ) ( -x + 5 )
= 3 * x + 3 * (-10) - [ x *(-x) + x * 5 + 2 * (-x) + 2 * 5 ]
= 3x - 30 - [ -x^2 + 5x - 2x + 10 ]
= 3x - 30 + x^2 + 3x + 10
= x^2 + 6x - 20

c = (3x + 5)²
= (3x)^2 + 2 * 3x * 5 + 5^2
= 9x^2 + 30x + 25