Répondre :
a= 2+(-3x+5)
= 2 -3x +5
= -3x +7
b= 7x-4-(x-3)
= 7x -4 -x +3
= 6x -1
c= 8x-(2-x)+(-7+4x)-(-9x+1)
= 8x -2 +x -7 +4x +9x -1
= 4x -10
*
a= 3(u+3)
= 3u + 9
b= 5(t-1)
= 5t -5
c= 5x(x-1)+x(3-5x)
= 5x² -5 +3x -5x²
= 3x -5
d= 2(a+b)-3(-a+b)
= 2a + 2b +3a -3b
= 5a -b