je n'arrive pas svp

la A= x(5-x)-3(x-5)
A= 5x-x au carré -3x+15
A= 2x-x au carré +15

B=(x-2)(5x-1)
= 5x au carré -x-10x+2
5x au carré -11x+2

C= (5x-2)(x+1)+(2x+3)(x-3)
= (5x au carré +5x-2x-2)+(2x au carré -6x+3x-9)
= 7x au carré -11

A = x ( 5 - x ) - 3 ( x - 5 ) 
A = 5x - x² - 3x + 15
A = - x² + 2x + 15

B = ( x - 2 ) ( 5x - 1 )
B = 5x² - 10x - x + 2
B = 5x² - 11x + 2 

C = ( 5x - 2 ) ( x + 1 ) + ( 2x + 3 ) ( x - 3 ) 
C = 5x² - 2x + 5x - 2 + 2x² + 3x - 6x - 9
C = 7x² - 11