bonjour
a) x(x - 4) + x²
=x*x-x*4+x²
=x²-4x+x²
=2x²-4x
b) x(2x + 5) - x
=x*2x+x*5-x
=2x²+5x-x
=2x²+4x
c) (x + 1)(x + 2)
=x*x+x*2+1*x+1*2
=x²+2x+1x+2
=x²+3x+2
d) (x + 5)(x - 1)
=x²-1x+5x-5
=x²+4x-5
e) (2x + 1)(3x + 1)
=6x²+2x+3x+1
=6x²+5x+1
f) (x - 3)(x - 4)
=x²-4x-3x+12
=x²-7x+12
*= multiplier