Bonjour,
(2x-5)(x+4)+(3x+7)² = 2x²+8x-5x-20+9x²+42x+49
= 11x²+45x+29
(6x+10)(6x-10)-(4x-3)² = (6x)²-10²-(16x²-24x+9)
= 36x²-16x²+24x-100-9
= 20x²+24x-109
