Bonsoir,
6(2x-5)² = 6(4x²-20x+25) = 24x²-120x+150
5x(x-8)+(x+2)(x-1) = 5x²-40x+x²-x+2x-2 = 6x²-39x-2
(2x-3)(2x+3)+(x-1)(3x+1) = 4x²-9+3x²+x-3x-1 = 7x²-2x-10
(5x+2)²-3(x+1) = 25x²+20x+4-3x-3 = 25x²+17x+1
(5x-1)(2x-3)-(6x+5)(x-4) = 10x²-15x-2x+3-(6x²-24x+5x-20)
= 10x²-6x²-15x-2x+24x-5x+3+20
= 4x²+2x+23
