Explications étape par étape:
f(x)=5(7x-9)
=5*7x-5*9
=35x-45
g(x)=a(-12a+5)
=a*(-12a)+a*5
=-12a²+5a
h(x)=-4b(9b-3)+1
= -4b*9b-4b*(-3)+1
=-36b²+12b+1
i(x) =(2x+8)*(7x+3)
=2x*7x+8*7x+2x*3+8*3
=14x²+56x+6x+24
=14x²+62x+24
j(x)=(9x-2)(6-5x)
=9x*6+9x*(-5x)-2*6-2*(-5x)
=54x-45x-12-10x
=-x-12
