б) (12a+b)(3a+5b)=36а^2+60аb+3аb+5b^2=36a^2+63ab+5b^2;
г) (5m - 2n)(3n - 5m)=15mn-25m^2-6n^2+10mn=-25m^2+25mn-6n^2;
е) (-7x -4y)(-5x+7y)=35x^2-49xy+20xy-28y^2= 35x^2-20xy -28y^2;
а) (8x-3)(4x+5)=32x^2+40x-12x-15= 32x^2+28x-15;
б) 8x-3*4x+5=8x-12x+5=-4x+5=5-4x;
в) (4a-3)*2a-3=8a^2-6a-3;
г) 4a-3 (2a-3)=4a-6a+9=-2a+9=9-2a;