d) (x + 3)² + (x - 4)² + 2(x - 3)(x + 3) =
= x² + 6x + 9 + x² - 8x + 16 + 2x² + 18
= 4x² - 2x + 7
e) (3x - 2)² + (2x + 3)² + 3 (x - 2)(x + 2) - 4x(x - 2) =
= 9x² - 12x + 4 + 4x² + 12x + 9 + 3
= 13x² + 16
f) (2x - 3)² - 3(2x - 1)(2x + 3) - 8(1 -x) =
= 4x² - 12x + 9 - 12x² - 18x + 6x + 9 - 8 + 8x
= - 8x² - 16x + 10