Решение
а) (3x - 28)/(x² - 16) + 2/(x - 4) = (3x - 28 + 2x + 8)/(x² - 25) =
= (5x - 20)/(x² - 25) = 5*(x - 4) / (x² - 25)
б) 3/(2x - 3) - 3/(2x + 3) - 8x² / (4x² - 9) =
= [3*(2x + 3) - 3*(2x - 3) - 8x²] / (4x² - 9) =
= (6x² + 9 - 6x² + 9 - 8x²) / (4x² - 9) =
= (18 - 8x²) / (4x² - 9) = [ -2*(4x² - 9)] / (4x² - 9) = - 2