Developpement et factorisation

[mssiss]

Est-ce que ces developpement sont juste?

A=(2x-5)²+(3x-2)(3x+2)
=(2x)²-2*2x*5+5²+9x²-2²
= 4x²-20x+25+9x²-4
=13x²-20x+21

B=(1-x)²-2(x-5)(1-4x)
=1²-2*1x+x²-2(1x-4x²-5+20x)
=1-2x+x²-2x+8x²+10-40x
=11-44x+9x²

C=3(2x-1)²-2(2-x)²
=3[(2x)²-2*2x*1+1²]-2(2²-2*2*x+x²)
=12x²-12x+1-8+8x+x²
=13x²-4x-7

Merci d'avance ...