(2x-3)(3x+7)-(x-5)(5x+6)-x/2=
=6x 2+14x-9x-21-(5x/2+6x-25x-30)-x 2=
=6x 2+14x-9x-21-5x 2-6x+25x+30-x 2=
=24x+9
При х=11/24
24×11/24+9=11+9=20
(2x-3)(3x+7)-(x-5)(5x+6)-x/2=
=6x 2+14x-9x-21-(5x/2+6x-25x-30)-x 2=
=6x 2+14x-9x-21-5x 2-6x+25x+30-x 2=
=24x+9
При х=11/24
24×11/24+9=11+9=20