х) +21. 17.9. 1) (x + 4,5)(6x - 1) - (3x + 1,6)(2x - 1) = -3,8x; 2) (3,5 - x)(7x + 2) + (3,5x - 1)(7 + 2x) = -450; 3) (8x+3)(1 - 0,9x) + 7,4 = (4x - 5)(1 - 1,8x); 4) 498 + (2,7 - 5x)(6x - 7) = (9 - 0,5x)(60x + 1). ​