(4x+3)(3-4x)+(3x-4)^2 - (19-16x) = (12х-16x^2+9-12х) + (3х-4)^2 - 19 +16х = -16х^2 +9 +(3x-4)^2 - 19+16х= - 16х^2 + 9x^2 - 16 - 10+16x= -7x^2 - 26 +16x